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2022-10-09Merge tag 'ucount-rlimits-cleanups-for-v5.19' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace Pull ucounts update from Eric Biederman: "Split rlimit and ucount values and max values After the ucount rlimit code was merged a bunch of small but siginificant bugs were found and fixed. At the time it was realized that part of the problem was that while the ucount rlimits were very similar to the oridinary ucounts (in being nested counts with limits) the semantics were slightly different and the code would be less error prone if there was less sharing. This is the long awaited cleanup that should hopefully keep things more comprehensible and less error prone for whoever needs to touch that code next" * tag 'ucount-rlimits-cleanups-for-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: ucounts: Split rlimit and ucount values and max values
2022-10-06Merge tag 'pull-file_inode' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs Pull file_inode() updates from Al Vrio: "whack-a-mole: cropped up open-coded file_inode() uses..." * tag 'pull-file_inode' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: orangefs: use ->f_mapping _nfs42_proc_copy(): use ->f_mapping instead of file_inode()->i_mapping dma_buf: no need to bother with file_inode()->i_mapping nfs_finish_open(): don't open-code file_inode() bprm_fill_uid(): don't open-code file_inode() sgx: use ->f_mapping... exfat_iterate(): don't open-code file_inode(file) ibmvmc: don't open-code file_inode()
2022-09-27a.out: Remove the a.out implementationEric W. Biederman
In commit 19e8b701e258 ("a.out: Stop building a.out/osf1 support on alpha and m68k") the last users of a.out were disabled. As nothing has turned up to cause this change to be reverted, let's remove the code implementing a.out support as well. There may be userspace users of the uapi bits left so the uapi headers have been left untouched. Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> Acked-by: Arnd Bergmann <arnd@arndb.de> # arm defconfigs Signed-off-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/871qrx3hq3.fsf@email.froward.int.ebiederm.org
2022-09-13Revert "fs/exec: allow to unshare a time namespace on vfork+exec"Andrei Vagin
This reverts commit 133e2d3e81de5d9706cab2dd1d52d231c27382e5. Alexey pointed out a few undesirable side effects of the reverted change. First, it doesn't take into account that CLONE_VFORK can be used with CLONE_THREAD. Second, a child process doesn't enter a target time name-space, if its parent dies before the child calls exec. It happens because the parent clears vfork_done. Eric W. Biederman suggests installing a time namespace as a task gets a new mm. It includes all new processes cloned without CLONE_VM and all tasks that call exec(). This is an user API change, but we think there aren't users that depend on the old behavior. It is too late to make such changes in this release, so let's roll back this patch and introduce the right one in the next release. Cc: Alexey Izbyshev <izbyshev@ispras.ru> Cc: Christian Brauner <brauner@kernel.org> Cc: Dmitry Safonov <0x7f454c46@gmail.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Florian Weimer <fweimer@redhat.com> Cc: Kees Cook <keescook@chromium.org> Signed-off-by: Andrei Vagin <avagin@gmail.com> Signed-off-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20220913102551.1121611-3-avagin@google.com
2022-09-01bprm_fill_uid(): don't open-code file_inode()Al Viro
Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2022-08-19Merge tag 'execve-v6.0-rc2' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux Pull execve fix from Kees Cook: - Replace remaining kmap() uses with kmap_local_page() (Fabio M. De Francesco) * tag 'execve-v6.0-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux: exec: Replace kmap{,_atomic}() with kmap_local_page()
2022-08-16exec: Replace kmap{,_atomic}() with kmap_local_page()Fabio M. De Francesco
The use of kmap() and kmap_atomic() are being deprecated in favor of kmap_local_page(). There are two main problems with kmap(): (1) It comes with an overhead as mapping space is restricted and protected by a global lock for synchronization and (2) it also requires global TLB invalidation when the kmap’s pool wraps and it might block when the mapping space is fully utilized until a slot becomes available. With kmap_local_page() the mappings are per thread, CPU local, can take page faults, and can be called from any context (including interrupts). It is faster than kmap() in kernels with HIGHMEM enabled. Furthermore, the tasks can be preempted and, when they are scheduled to run again, the kernel virtual addresses are restored and are still valid. Since the use of kmap_local_page() in exec.c is safe, it should be preferred everywhere in exec.c. As said, since kmap_local_page() can be also called from atomic context, and since remove_arg_zero() doesn't (and shouldn't ever) rely on an implicit preempt_disable(), this function can also safely replace kmap_atomic(). Therefore, replace kmap() and kmap_atomic() with kmap_local_page() in fs/exec.c. Tested with xfstests on a QEMU/KVM x86_32 VM, 6GB RAM, booting a kernel with HIGHMEM64GB enabled. Cc: Eric W. Biederman <ebiederm@xmission.com> Suggested-by: Ira Weiny <ira.weiny@intel.com> Reviewed-by: Ira Weiny <ira.weiny@intel.com> Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com> Signed-off-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20220803182856.28246-1-fmdefrancesco@gmail.com
2022-08-09posix-cpu-timers: Cleanup CPU timers before freeing them during execThadeu Lima de Souza Cascardo
Commit 55e8c8eb2c7b ("posix-cpu-timers: Store a reference to a pid not a task") started looking up tasks by PID when deleting a CPU timer. When a non-leader thread calls execve, it will switch PIDs with the leader process. Then, as it calls exit_itimers, posix_cpu_timer_del cannot find the task because the timer still points out to the old PID. That means that armed timers won't be disarmed, that is, they won't be removed from the timerqueue_list. exit_itimers will still release their memory, and when that list is later processed, it leads to a use-after-free. Clean up the timers from the de-threaded task before freeing them. This prevents a reported use-after-free. Fixes: 55e8c8eb2c7b ("posix-cpu-timers: Store a reference to a pid not a task") Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Cc: <stable@vger.kernel.org> Link: https://lore.kernel.org/r/20220809170751.164716-1-cascardo@canonical.com
2022-08-02Merge tag 'execve-v5.20-rc1' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux Pull execve updates from Kees Cook: - Allow unsharing time namespace on vfork+exec (Andrei Vagin) - Replace usage of deprecated kmap APIs (Fabio M. De Francesco) - Fix spelling mistake (Zhang Jiaming) * tag 'execve-v5.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux: exec: Call kmap_local_page() in copy_string_kernel() exec: Fix a spelling mistake selftests/timens: add a test for vfork+exit fs/exec: allow to unshare a time namespace on vfork+exec
2022-07-27exec: Call kmap_local_page() in copy_string_kernel()Fabio M. De Francesco
The use of kmap_atomic() is being deprecated in favor of kmap_local_page(). With kmap_local_page(), the mappings are per thread, CPU local and not globally visible. Furthermore, the mappings can be acquired from any context (including interrupts). Therefore, replace kmap_atomic() with kmap_local_page() in copy_string_kernel(). Instead of open-coding local mapping + memcpy(), use memcpy_to_page(). Delete a redundant call to flush_dcache_page(). Tested with xfstests on a QEMU/ KVM x86_32 VM, 6GB RAM, booting a kernel with HIGHMEM64GB enabled. Suggested-by: Ira Weiny <ira.weiny@intel.com> Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com> Signed-off-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20220724212523.13317-1-fmdefrancesco@gmail.com
2022-07-11fix race between exit_itimers() and /proc/pid/timersOleg Nesterov
As Chris explains, the comment above exit_itimers() is not correct, we can race with proc_timers_seq_ops. Change exit_itimers() to clear signal->posix_timers with ->siglock held. Cc: <stable@vger.kernel.org> Reported-by: chris@accessvector.net Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2022-07-01exec: Fix a spelling mistakeZhang Jiaming
Change 'wont't' to 'won't'. Signed-off-by: Zhang Jiaming <jiaming@nfschina.com> Reviewed-by: Souptick Joarder (HPE) <jrdr.linux@gmail.com> Signed-off-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20220629072932.27506-1-jiaming@nfschina.com
2022-06-15fs/exec: allow to unshare a time namespace on vfork+execAndrei Vagin
Right now, a new process can't be forked in another time namespace if it shares mm with its parent. It is prohibited, because each time namespace has its own vvar page that is mapped into a process address space. When a process calls exec, it gets a new mm and so it could be "legal" to switch time namespace in that case. This was not implemented and now if we want to do this, we need to add another clone flag to not break backward compatibility. We don't have any user requests to switch times on exec except the vfork+exec combination, so there is no reason to add a new clone flag. As for vfork+exec, this should be safe to allow switching timens with the current clone flag. Right now, vfork (CLONE_VFORK | CLONE_VM) fails if a child is forked into another time namespace. With this change, vfork creates a new process in parent's timens, and the following exec does the actual switch to the target time namespace. Suggested-by: Florian Weimer <fweimer@redhat.com> Signed-off-by: Andrei Vagin <avagin@gmail.com> Acked-by: Christian Brauner (Microsoft) <brauner@kernel.org> Signed-off-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20220613060723.197407-1-avagin@gmail.com
2022-06-03Merge tag 'kthread-cleanups-for-v5.19' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace Pull kthread updates from Eric Biederman: "This updates init and user mode helper tasks to be ordinary user mode tasks. Commit 40966e316f86 ("kthread: Ensure struct kthread is present for all kthreads") caused init and the user mode helper threads that call kernel_execve to have struct kthread allocated for them. This struct kthread going away during execve in turned made a use after free of struct kthread possible. Here, commit 343f4c49f243 ("kthread: Don't allocate kthread_struct for init and umh") is enough to fix the use after free and is simple enough to be backportable. The rest of the changes pass struct kernel_clone_args to clean things up and cause the code to make sense. In making init and the user mode helpers tasks purely user mode tasks I ran into two complications. The function task_tick_numa was detecting tasks without an mm by testing for the presence of PF_KTHREAD. The initramfs code in populate_initrd_image was using flush_delayed_fput to ensuere the closing of all it's file descriptors was complete, and flush_delayed_fput does not work in a userspace thread. I have looked and looked and more complications and in my code review I have not found any, and neither has anyone else with the code sitting in linux-next" * tag 'kthread-cleanups-for-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: sched: Update task_tick_numa to ignore tasks without an mm fork: Stop allowing kthreads to call execve fork: Explicitly set PF_KTHREAD init: Deal with the init process being a user mode process fork: Generalize PF_IO_WORKER handling fork: Explicity test for idle tasks in copy_thread fork: Pass struct kernel_clone_args into copy_thread kthread: Don't allocate kthread_struct for init and umh
2022-05-18ucounts: Split rlimit and ucount values and max valuesAlexey Gladkov
Since the semantics of maximum rlimit values are different, it would be better not to mix ucount and rlimit values. This will prevent the error of using inc_count/dec_ucount for rlimit parameters. This patch also renames the functions to emphasize the lack of connection between rlimit and ucount. v3: - Fix BUG:KASAN:use-after-free_in_dec_ucount. v2: - Fix the array-index-out-of-bounds that was found by the lkp project. Reported-by: kernel test robot <oliver.sang@intel.com> Signed-off-by: Alexey Gladkov <legion@kernel.org> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Link: https://lkml.kernel.org/r/20220518171730.l65lmnnjtnxnftpq@example.org Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2022-05-13mm/mprotect: use mmu_gatherNadav Amit
Patch series "mm/mprotect: avoid unnecessary TLB flushes", v6. This patchset is intended to remove unnecessary TLB flushes during mprotect() syscalls. Once this patch-set make it through, similar and further optimizations for MADV_COLD and userfaultfd would be possible. Basically, there are 3 optimizations in this patch-set: 1. Use TLB batching infrastructure to batch flushes across VMAs and do better/fewer flushes. This would also be handy for later userfaultfd enhancements. 2. Avoid unnecessary TLB flushes. This optimization is the one that provides most of the performance benefits. Unlike previous versions, we now only avoid flushes that would not result in spurious page-faults. 3. Avoiding TLB flushes on change_huge_pmd() that are only needed to prevent the A/D bits from changing. Andrew asked for some benchmark numbers. I do not have an easy determinate macrobenchmark in which it is easy to show benefit. I therefore ran a microbenchmark: a loop that does the following on anonymous memory, just as a sanity check to see that time is saved by avoiding TLB flushes. The loop goes: mprotect(p, PAGE_SIZE, PROT_READ) mprotect(p, PAGE_SIZE, PROT_READ|PROT_WRITE) *p = 0; // make the page writable The test was run in KVM guest with 1 or 2 threads (the second thread was busy-looping). I measured the time (cycles) of each operation: 1 thread 2 threads mmots +patch mmots +patch PROT_READ 3494 2725 (-22%) 8630 7788 (-10%) PROT_READ|WRITE 3952 2724 (-31%) 9075 2865 (-68%) [ mmots = v5.17-rc6-mmots-2022-03-06-20-38 ] The exact numbers are really meaningless, but the benefit is clear. There are 2 interesting results though. (1) PROT_READ is cheaper, while one can expect it not to be affected. This is presumably due to TLB miss that is saved (2) Without memory access (*p = 0), the speedup of the patch is even greater. In that scenario mprotect(PROT_READ) also avoids the TLB flush. As a result both operations on the patched kernel take roughly ~1500 cycles (with either 1 or 2 threads), whereas on mmotm their cost is as high as presented in the table. This patch (of 3): change_pXX_range() currently does not use mmu_gather, but instead implements its own deferred TLB flushes scheme. This both complicates the code, as developers need to be aware of different invalidation schemes, and prevents opportunities to avoid TLB flushes or perform them in finer granularity. The use of mmu_gather for modified PTEs has benefits in various scenarios even if pages are not released. For instance, if only a single page needs to be flushed out of a range of many pages, only that page would be flushed. If a THP page is flushed, on x86 a single TLB invlpg instruction can be used instead of 512 instructions (or a full TLB flush, which would Linux would actually use by default). mprotect() over multiple VMAs requires a single flush. Use mmu_gather in change_pXX_range(). As the pages are not released, only record the flushed range using tlb_flush_pXX_range(). Handle THP similarly and get rid of flush_cache_range() which becomes redundant since tlb_start_vma() calls it when needed. Link: https://lkml.kernel.org/r/20220401180821.1986781-1-namit@vmware.com Link: https://lkml.kernel.org/r/20220401180821.1986781-2-namit@vmware.com Signed-off-by: Nadav Amit <namit@vmware.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Andrew Cooper <andrew.cooper3@citrix.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Peter Xu <peterx@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Will Deacon <will@kernel.org> Cc: Yu Zhao <yuzhao@google.com> Cc: Nick Piggin <npiggin@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2022-05-07fork: Stop allowing kthreads to call execveEric W. Biederman
Now that kernel_execve is no longer called from kernel threads stop supporting kernel threads calling kernel_execve. Remove the code for converting a kthread to a normal thread in execve. Document the restriction that kthreads may not call kernel_execve by having kernel_execve fail if called by a kthread. Link: https://lkml.kernel.org/r/20220506141512.516114-7-ebiederm@xmission.com Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2022-05-06kthread: Don't allocate kthread_struct for init and umhEric W. Biederman
If kthread_is_per_cpu runs concurrently with free_kthread_struct the kthread_struct that was just freed may be read from. This bug was introduced by commit 40966e316f86 ("kthread: Ensure struct kthread is present for all kthreads"). When kthread_struct started to be allocated for all tasks that have PF_KTHREAD set. This in turn required the kthread_struct to be freed in kernel_execve and violated the assumption that kthread_struct will have the same lifetime as the task. Looking a bit deeper this only applies to callers of kernel_execve which is just the init process and the user mode helper processes. These processes really don't want to be kernel threads but are for historical reasons. Mostly that copy_thread does not know how to take a kernel mode function to the process with for processes without PF_KTHREAD or PF_IO_WORKER set. Solve this by not allocating kthread_struct for the init process and the user mode helper processes. This is done by adding a kthread member to struct kernel_clone_args. Setting kthread in fork_idle and kernel_thread. Adding user_mode_thread that works like kernel_thread except it does not set kthread. In fork only allocating the kthread_struct if .kthread is set. I have looked at kernel/kthread.c and since commit 40966e316f86 ("kthread: Ensure struct kthread is present for all kthreads") there have been no assumptions added that to_kthread or __to_kthread will not return NULL. There are a few callers of to_kthread or __to_kthread that assume a non-NULL struct kthread pointer will be returned. These functions are kthread_data(), kthread_parmme(), kthread_exit(), kthread(), kthread_park(), kthread_unpark(), kthread_stop(). All of those functions can reasonably expected to be called when it is know that a task is a kthread so that assumption seems reasonable. Cc: stable@vger.kernel.org Fixes: 40966e316f86 ("kthread: Ensure struct kthread is present for all kthreads") Reported-by: Максим Кутявин <maximkabox13@gmail.com> Link: https://lkml.kernel.org/r/20220506141512.516114-1-ebiederm@xmission.com Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2022-03-28Merge tag 'ptrace-cleanups-for-v5.18' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace Pull ptrace cleanups from Eric Biederman: "This set of changes removes tracehook.h, moves modification of all of the ptrace fields inside of siglock to remove races, adds a missing permission check to ptrace.c The removal of tracehook.h is quite significant as it has been a major source of confusion in recent years. Much of that confusion was around task_work and TIF_NOTIFY_SIGNAL (which I have now decoupled making the semantics clearer). For people who don't know tracehook.h is a vestiage of an attempt to implement uprobes like functionality that was never fully merged, and was later superseeded by uprobes when uprobes was merged. For many years now we have been removing what tracehook functionaly a little bit at a time. To the point where anything left in tracehook.h was some weird strange thing that was difficult to understand" * tag 'ptrace-cleanups-for-v5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: ptrace: Remove duplicated include in ptrace.c ptrace: Check PTRACE_O_SUSPEND_SECCOMP permission on PTRACE_SEIZE ptrace: Return the signal to continue with from ptrace_stop ptrace: Move setting/clearing ptrace_message into ptrace_stop tracehook: Remove tracehook.h resume_user_mode: Move to resume_user_mode.h resume_user_mode: Remove #ifdef TIF_NOTIFY_RESUME in set_notify_resume signal: Move set_notify_signal and clear_notify_signal into sched/signal.h task_work: Decouple TIF_NOTIFY_SIGNAL and task_work task_work: Call tracehook_notify_signal from get_signal on all architectures task_work: Introduce task_work_pending task_work: Remove unnecessary include from posix_timers.h ptrace: Remove tracehook_signal_handler ptrace: Remove arch_syscall_{enter,exit}_tracehook ptrace: Create ptrace_report_syscall_{entry,exit} in ptrace.h ptrace/arm: Rename tracehook_report_syscall report_syscall ptrace: Move ptrace_report_syscall into ptrace.h
2022-03-23Merge tag 'asm-generic-5.18' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic Pull asm-generic updates from Arnd Bergmann: "There are three sets of updates for 5.18 in the asm-generic tree: - The set_fs()/get_fs() infrastructure gets removed for good. This was already gone from all major architectures, but now we can finally remove it everywhere, which loses some particularly tricky and error-prone code. There is a small merge conflict against a parisc cleanup, the solution is to use their new version. - The nds32 architecture ends its tenure in the Linux kernel. The hardware is still used and the code is in reasonable shape, but the mainline port is not actively maintained any more, as all remaining users are thought to run vendor kernels that would never be updated to a future release. - A series from Masahiro Yamada cleans up some of the uapi header files to pass the compile-time checks" * tag 'asm-generic-5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic: (27 commits) nds32: Remove the architecture uaccess: remove CONFIG_SET_FS ia64: remove CONFIG_SET_FS support sh: remove CONFIG_SET_FS support sparc64: remove CONFIG_SET_FS support lib/test_lockup: fix kernel pointer check for separate address spaces uaccess: generalize access_ok() uaccess: fix type mismatch warnings from access_ok() arm64: simplify access_ok() m68k: fix access_ok for coldfire MIPS: use simpler access_ok() MIPS: Handle address errors for accesses above CPU max virtual user address uaccess: add generic __{get,put}_kernel_nofault nios2: drop access_ok() check from __put_user() x86: use more conventional access_ok() definition x86: remove __range_not_ok() sparc64: add __{get,put}_kernel_nofault() nds32: fix access_ok() checks in get/put_user uaccess: fix nios2 and microblaze get_user_8() sparc64: fix building assembly files ...
2022-03-10tracehook: Remove tracehook.hEric W. Biederman
Now that all of the definitions have moved out of tracehook.h into ptrace.h, sched/signal.h, resume_user_mode.h there is nothing left in tracehook.h so remove it. Update the few files that were depending upon tracehook.h to bring in definitions to use the headers they need directly. Reviewed-by: Kees Cook <keescook@chromium.org> Link: https://lkml.kernel.org/r/20220309162454.123006-13-ebiederm@xmission.com Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2022-03-01exec: cleanup commentsTom Rix
Remove the second 'from'. Replace 'backwords' with 'backwards'. Replace 'visibile' with 'visible'. Signed-off-by: Tom Rix <trix@redhat.com> Acked-by: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20220211160940.2516243-1-trix@redhat.com
2022-03-01exec: Force single empty string when argv is emptyKees Cook
Quoting[1] Ariadne Conill: "In several other operating systems, it is a hard requirement that the second argument to execve(2) be the name of a program, thus prohibiting a scenario where argc < 1. POSIX 2017 also recommends this behaviour, but it is not an explicit requirement[2]: The argument arg0 should point to a filename string that is associated with the process being started by one of the exec functions. ... Interestingly, Michael Kerrisk opened an issue about this in 2008[3], but there was no consensus to support fixing this issue then. Hopefully now that CVE-2021-4034 shows practical exploitative use[4] of this bug in a shellcode, we can reconsider. This issue is being tracked in the KSPP issue tracker[5]." While the initial code searches[6][7] turned up what appeared to be mostly corner case tests, trying to that just reject argv == NULL (or an immediately terminated pointer list) quickly started tripping[8] existing userspace programs. The next best approach is forcing a single empty string into argv and adjusting argc to match. The number of programs depending on argc == 0 seems a smaller set than those calling execve with a NULL argv. Account for the additional stack space in bprm_stack_limits(). Inject an empty string when argc == 0 (and set argc = 1). Warn about the case so userspace has some notice about the change: process './argc0' launched './argc0' with NULL argv: empty string added Additionally WARN() and reject NULL argv usage for kernel threads. [1] https://lore.kernel.org/lkml/20220127000724.15106-1-ariadne@dereferenced.org/ [2] https://pubs.opengroup.org/onlinepubs/9699919799/functions/exec.html [3] https://bugzilla.kernel.org/show_bug.cgi?id=8408 [4] https://www.qualys.com/2022/01/25/cve-2021-4034/pwnkit.txt [5] https://github.com/KSPP/linux/issues/176 [6] https://codesearch.debian.net/search?q=execve%5C+*%5C%28%5B%5E%2C%5D%2B%2C+*NULL&literal=0 [7] https://codesearch.debian.net/search?q=execlp%3F%5Cs*%5C%28%5B%5E%2C%5D%2B%2C%5Cs*NULL&literal=0 [8] https://lore.kernel.org/lkml/20220131144352.GE16385@xsang-OptiPlex-9020/ Reported-by: Ariadne Conill <ariadne@dereferenced.org> Reported-by: Michael Kerrisk <mtk.manpages@gmail.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Christian Brauner <brauner@kernel.org> Cc: Rich Felker <dalias@libc.org> Cc: Eric Biederman <ebiederm@xmission.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: linux-fsdevel@vger.kernel.org Cc: stable@vger.kernel.org Signed-off-by: Kees Cook <keescook@chromium.org> Acked-by: Christian Brauner <brauner@kernel.org> Acked-by: Ariadne Conill <ariadne@dereferenced.org> Acked-by: Andy Lutomirski <luto@kernel.org> Link: https://lore.kernel.org/r/20220201000947.2453721-1-keescook@chromium.org
2022-02-25uaccess: remove CONFIG_SET_FSArnd Bergmann
There are no remaining callers of set_fs(), so CONFIG_SET_FS can be removed globally, along with the thread_info field and any references to it. This turns access_ok() into a cheaper check against TASK_SIZE_MAX. As CONFIG_SET_FS is now gone, drop all remaining references to set_fs()/get_fs(), mm_segment_t, user_addr_max() and uaccess_kernel(). Acked-by: Sam Ravnborg <sam@ravnborg.org> # for sparc32 changes Acked-by: "Eric W. Biederman" <ebiederm@xmission.com> Tested-by: Sergey Matyukevich <sergey.matyukevich@synopsys.com> # for arc changes Acked-by: Stafford Horne <shorne@gmail.com> # [openrisc, asm-generic] Acked-by: Dinh Nguyen <dinguyen@kernel.org> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
2022-01-22fs/coredump: move coredump sysctls into its own fileXiaoming Ni
This moves the fs/coredump.c respective sysctls to its own file. Link: https://lkml.kernel.org/r/20211129211943.640266-6-mcgrof@kernel.org Signed-off-by: Xiaoming Ni <nixiaoming@huawei.com> Signed-off-by: Luis Chamberlain <mcgrof@kernel.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com> Cc: Antti Palosaari <crope@iki.fi> Cc: Christian Brauner <christian.brauner@ubuntu.com> Cc: "David S. Miller" <davem@davemloft.net> Cc: Eric Biederman <ebiederm@xmission.com> Cc: Eric Biggers <ebiggers@google.com> Cc: Iurii Zaikin <yzaikin@google.com> Cc: Kees Cook <keescook@chromium.org> Cc: Lukas Middendorf <kernel@tuxforce.de> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com> Cc: Stephen Kitt <steve@sk2.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2022-01-22fs: move fs/exec.c sysctls into its own fileLuis Chamberlain
kernel/sysctl.c is a kitchen sink where everyone leaves their dirty dishes, this makes it very difficult to maintain. To help with this maintenance let's start by moving sysctls to places where they actually belong. The proc sysctl maintainers do not want to know what sysctl knobs you wish to add for your own piece of code, we just care about the core logic. So move the fs/exec.c respective sysctls to its own file. Since checkpatch complains about style issues with the old code, this move also fixes a few of those minor style issues: * Use pr_warn() instead of prink(WARNING * New empty lines are wanted at the beginning of routines Link: https://lkml.kernel.org/r/20211129205548.605569-9-mcgrof@kernel.org Signed-off-by: Luis Chamberlain <mcgrof@kernel.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Cc: Antti Palosaari <crope@iki.fi> Cc: Eric Biederman <ebiederm@xmission.com> Cc: Iurii Zaikin <yzaikin@google.com> Cc: "J. Bruce Fields" <bfields@fieldses.org> Cc: Jeff Layton <jlayton@kernel.org> Cc: Kees Cook <keescook@chromium.org> Cc: Lukas Middendorf <kernel@tuxforce.de> Cc: Stephen Kitt <steve@sk2.org> Cc: Xiaoming Ni <nixiaoming@huawei.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2022-01-20Merge branch 'akpm' (patches from Andrew)Linus Torvalds
Merge more updates from Andrew Morton: "55 patches. Subsystems affected by this patch series: percpu, procfs, sysctl, misc, core-kernel, get_maintainer, lib, checkpatch, binfmt, nilfs2, hfs, fat, adfs, panic, delayacct, kconfig, kcov, and ubsan" * emailed patches from Andrew Morton <akpm@linux-foundation.org>: (55 commits) lib: remove redundant assignment to variable ret ubsan: remove CONFIG_UBSAN_OBJECT_SIZE kcov: fix generic Kconfig dependencies if ARCH_WANTS_NO_INSTR lib/Kconfig.debug: make TEST_KMOD depend on PAGE_SIZE_LESS_THAN_256KB btrfs: use generic Kconfig option for 256kB page size limit arch/Kconfig: split PAGE_SIZE_LESS_THAN_256KB from PAGE_SIZE_LESS_THAN_64KB configs: introduce debug.config for CI-like setup delayacct: track delays from memory compact Documentation/accounting/delay-accounting.rst: add thrashing page cache and direct compact delayacct: cleanup flags in struct task_delay_info and functions use it delayacct: fix incomplete disable operation when switch enable to disable delayacct: support swapin delay accounting for swapping without blkio panic: remove oops_id panic: use error_report_end tracepoint on warnings fs/adfs: remove unneeded variable make code cleaner FAT: use io_schedule_timeout() instead of congestion_wait() hfsplus: use struct_group_attr() for memcpy() region nilfs2: remove redundant pointer sbufs fs/binfmt_elf: use PT_LOAD p_align values for static PIE const_structs.checkpatch: add frequently used ops structs ...
2022-01-20fs/exec: replace strncpy with strscpy_pad in __get_task_commYafang Shao
If the dest buffer size is smaller than sizeof(tsk->comm), the buffer will be without null ternimator, that may cause problem. Using strscpy_pad() instead of strncpy() in __get_task_comm() can make the string always nul ternimated and zero padded. Link: https://lkml.kernel.org/r/20211120112738.45980-3-laoar.shao@gmail.com Suggested-by: Kees Cook <keescook@chromium.org> Suggested-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Yafang Shao <laoar.shao@gmail.com> Reviewed-by: Kees Cook <keescook@chromium.org> Reviewed-by: David Hildenbrand <david@redhat.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com> Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com> Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com> Cc: Michal Miroslaw <mirq-linux@rere.qmqm.pl> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Matthew Wilcox <willy@infradead.org> Cc: David Hildenbrand <david@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Kees Cook <keescook@chromium.org> Cc: Petr Mladek <pmladek@suse.com> Cc: Andrii Nakryiko <andrii@kernel.org> Cc: Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2022-01-20fs/exec: replace strlcpy with strscpy_pad in __set_task_commYafang Shao
Patch series "task comm cleanups", v2. This patchset is part of the patchset "extend task comm from 16 to 24"[1]. Now we have different opinion that dynamically allocates memory to store kthread's long name into a separate pointer, so I decide to take the useful cleanups apart from the original patchset and send it separately[2]. These useful cleanups can make the usage around task comm less error-prone. Furthermore, it will be useful if we want to extend task comm in the future. [1]. https://lore.kernel.org/lkml/20211101060419.4682-1-laoar.shao@gmail.com/ [2]. https://lore.kernel.org/lkml/CALOAHbAx55AUo3bm8ZepZSZnw7A08cvKPdPyNTf=E_tPqmw5hw@mail.gmail.com/ This patch (of 7): strlcpy() can trigger out-of-bound reads on the source string[1], we'd better use strscpy() instead. To make it be robust against full tsk->comm copies that got noticed in other places, we should make sure it's zero padded. [1] https://github.com/KSPP/linux/issues/89 Link: https://lkml.kernel.org/r/20211120112738.45980-1-laoar.shao@gmail.com Link: https://lkml.kernel.org/r/20211120112738.45980-2-laoar.shao@gmail.com Signed-off-by: Yafang Shao <laoar.shao@gmail.com> Reviewed-by: Kees Cook <keescook@chromium.org> Reviewed-by: David Hildenbrand <david@redhat.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com> Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com> Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com> Cc: Michal Miroslaw <mirq-linux@rere.qmqm.pl> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Matthew Wilcox <willy@infradead.org> Cc: David Hildenbrand <david@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Kees Cook <keescook@chromium.org> Cc: Petr Mladek <pmladek@suse.com> Cc: Andrii Nakryiko <andrii@kernel.org> Cc: Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2022-01-08signal: Remove the helper signal_group_exitEric W. Biederman
This helper is misleading. It tests for an ongoing exec as well as the process having received a fatal signal. Sometimes it is appropriate to treat an on-going exec differently than a process that is shutting down due to a fatal signal. In particular taking the fast path out of exit_signals instead of retargeting signals is not appropriate during exec, and not changing the the exit code in do_group_exit during exec. Removing the helper makes it more obvious what is going on as both cases must be coded for explicitly. While removing the helper fix the two cases where I have observed using signal_group_exit resulted in the wrong result. In exit_signals only test for SIGNAL_GROUP_EXIT so that signals are retargetted during an exec. In do_group_exit use 0 as the exit code during an exec as de_thread does not set group_exit_code. As best as I can determine group_exit_code has been is set to 0 most of the time during de_thread. During a thread group stop group_exit_code is set to the stop signal and when the thread group receives SIGCONT group_exit_code is reset to 0. Link: https://lkml.kernel.org/r/20211213225350.27481-8-ebiederm@xmission.com Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2022-01-08signal: Rename group_exit_task group_exec_taskEric W. Biederman
The only remaining user of group_exit_task is exec. Rename the field so that it is clear which part of the code uses it. Update the comment above the definition of group_exec_task to document how it is currently used. Link: https://lkml.kernel.org/r/20211213225350.27481-7-ebiederm@xmission.com Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2021-12-13kthread: Ensure struct kthread is present for all kthreadsEric W. Biederman
Today the rules are a bit iffy and arbitrary about which kernel threads have struct kthread present. Both idle threads and thread started with create_kthread want struct kthread present so that is effectively all kernel threads. Make the rule that if PF_KTHREAD and the task is running then struct kthread is present. This will allow the kernel thread code to using tsk->exit_code with different semantics from ordinary processes. To make ensure that struct kthread is present for all kernel threads move it's allocation into copy_process. Add a deallocation of struct kthread in exec for processes that were kernel threads. Move the allocation of struct kthread for the initial thread earlier so that it is not repeated for each additional idle thread. Move the initialization of struct kthread into set_kthread_struct so that the structure is always and reliably initailized. Clear set_child_tid in free_kthread_struct to ensure the kthread struct is reliably freed during exec. The function free_kthread_struct does not need to clear vfork_done during exec as exec_mm_release called from exec_mmap has already cleared vfork_done. Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2021-11-10Merge branch 'exit-cleanups-for-v5.16' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace Pull exit cleanups from Eric Biederman: "While looking at some issues related to the exit path in the kernel I found several instances where the code is not using the existing abstractions properly. This set of changes introduces force_fatal_sig a way of sending a signal and not allowing it to be caught, and corrects the misuse of the existing abstractions that I found. A lot of the misuse of the existing abstractions are silly things such as doing something after calling a no return function, rolling BUG by hand, doing more work than necessary to terminate a kernel thread, or calling do_exit(SIGKILL) instead of calling force_sig(SIGKILL). In the review a deficiency in force_fatal_sig and force_sig_seccomp where ptrace or sigaction could prevent the delivery of the signal was found. I have added a change that adds SA_IMMUTABLE to change that makes it impossible to interrupt the delivery of those signals, and allows backporting to fix force_sig_seccomp And Arnd found an issue where a function passed to kthread_run had the wrong prototype, and after my cleanup was failing to build." * 'exit-cleanups-for-v5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (23 commits) soc: ti: fix wkup_m3_rproc_boot_thread return type signal: Add SA_IMMUTABLE to ensure forced siganls do not get changed signal: Replace force_sigsegv(SIGSEGV) with force_fatal_sig(SIGSEGV) exit/r8188eu: Replace the macro thread_exit with a simple return 0 exit/rtl8712: Replace the macro thread_exit with a simple return 0 exit/rtl8723bs: Replace the macro thread_exit with a simple return 0 signal/x86: In emulate_vsyscall force a signal instead of calling do_exit signal/sparc32: In setup_rt_frame and setup_fram use force_fatal_sig signal/sparc32: Exit with a fatal signal when try_to_clear_window_buffer fails exit/syscall_user_dispatch: Send ordinary signals on failure signal: Implement force_fatal_sig exit/kthread: Have kernel threads return instead of calling do_exit signal/s390: Use force_sigsegv in default_trap_handler signal/vm86_32: Properly send SIGSEGV when the vm86 state cannot be saved. signal/vm86_32: Replace open coded BUG_ON with an actual BUG_ON signal/sparc: In setup_tsb_params convert open coded BUG into BUG signal/powerpc: On swapcontext failure force SIGSEGV signal/sh: Use force_sig(SIGKILL) instead of do_group_exit(SIGKILL) signal/mips: Update (_save|_restore)_fp_context to fail with -EFAULT signal/sparc32: Remove unreachable do_exit in do_sparc_fault ...
2021-10-29signal: Replace force_sigsegv(SIGSEGV) with force_fatal_sig(SIGSEGV)Eric W. Biederman
Now that force_fatal_sig exists it is unnecessary and a bit confusing to use force_sigsegv in cases where the simpler force_fatal_sig is wanted. So change every instance we can to make the code clearer. Acked-by: Geert Uytterhoeven <geert@linux-m68k.org> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org> Link: https://lkml.kernel.org/r/877de7jrev.fsf@disp2133 Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2021-10-06exec: Check for a pending fatal signal instead of core_stateEric W. Biederman
Prevent exec continuing when a fatal signal is pending by replacing mmap_read_lock with mmap_read_lock_killable. This is always the right thing to do as userspace will never observe an exec complete when there is a fatal signal pending. With that change it becomes unnecessary to explicitly test for a core dump in progress. In coredump_wait zap_threads arranges under mmap_write_lock for all tasks that use a mm to also have SIGKILL pending, which means mmap_read_lock_killable will always return -EINTR when old_mm->core_state is present. Link: https://lkml.kernel.org/r/87fstux27w.fsf@disp2133 Reviewed-by: Kees Cook <keescook@chromium.org> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2021-09-04Merge tag 'denywrite-for-5.15' of git://github.com/davidhildenbrand/linuxLinus Torvalds
Pull MAP_DENYWRITE removal from David Hildenbrand: "Remove all in-tree usage of MAP_DENYWRITE from the kernel and remove VM_DENYWRITE. There are some (minor) user-visible changes: - We no longer deny write access to shared libaries loaded via legacy uselib(); this behavior matches modern user space e.g. dlopen(). - We no longer deny write access to the elf interpreter after exec completed, treating it just like shared libraries (which it often is). - We always deny write access to the file linked via /proc/pid/exe: sys_prctl(PR_SET_MM_MAP/EXE_FILE) will fail if write access to the file cannot be denied, and write access to the file will remain denied until the link is effectivel gone (exec, termination, sys_prctl(PR_SET_MM_MAP/EXE_FILE)) -- just as if exec'ing the file. Cross-compiled for a bunch of architectures (alpha, microblaze, i386, s390x, ...) and verified via ltp that especially the relevant tests (i.e., creat07 and execve04) continue working as expected" * tag 'denywrite-for-5.15' of git://github.com/davidhildenbrand/linux: fs: update documentation of get_write_access() and friends mm: ignore MAP_DENYWRITE in ksys_mmap_pgoff() mm: remove VM_DENYWRITE binfmt: remove in-tree usage of MAP_DENYWRITE kernel/fork: always deny write access to current MM exe_file kernel/fork: factor out replacing the current MM exe_file binfmt: don't use MAP_DENYWRITE when loading shared libraries via uselib()
2021-09-03Merge branch 'akpm' (patches from Andrew)Linus Torvalds
Merge misc updates from Andrew Morton: "173 patches. Subsystems affected by this series: ia64, ocfs2, block, and mm (debug, pagecache, gup, swap, shmem, memcg, selftests, pagemap, mremap, bootmem, sparsemem, vmalloc, kasan, pagealloc, memory-failure, hugetlb, userfaultfd, vmscan, compaction, mempolicy, memblock, oom-kill, migration, ksm, percpu, vmstat, and madvise)" * emailed patches from Andrew Morton <akpm@linux-foundation.org>: (173 commits) mm/madvise: add MADV_WILLNEED to process_madvise() mm/vmstat: remove unneeded return value mm/vmstat: simplify the array size calculation mm/vmstat: correct some wrong comments mm/percpu,c: remove obsolete comments of pcpu_chunk_populated() selftests: vm: add COW time test for KSM pages selftests: vm: add KSM merging time test mm: KSM: fix data type selftests: vm: add KSM merging across nodes test selftests: vm: add KSM zero page merging test selftests: vm: add KSM unmerge test selftests: vm: add KSM merge test mm/migrate: correct kernel-doc notation mm: wire up syscall process_mrelease mm: introduce process_mrelease system call memblock: make memblock_find_in_range method private mm/mempolicy.c: use in_task() in mempolicy_slab_node() mm/mempolicy: unify the create() func for bind/interleave/prefer-many policies mm/mempolicy: advertise new MPOL_PREFERRED_MANY mm/hugetlb: add support for mempolicy MPOL_PREFERRED_MANY ...
2021-09-03mm/pagemap: add mmap_assert_locked() annotations to find_vma*()Luigi Rizzo
find_vma() and variants need protection when used. This patch adds mmap_assert_lock() calls in the functions. To make sure the invariant is satisfied, we also need to add a mmap_read_lock() around the get_user_pages_remote() call in get_arg_page(). The lock is not strictly necessary because the mm has been newly created, but the extra cost is limited because the same mutex was also acquired shortly before in __bprm_mm_init(), so it is hot and uncontended. [penguin-kernel@i-love.sakura.ne.jp: TOMOYO needs the same protection which get_arg_page() needs] Link: https://lkml.kernel.org/r/58bb6bf7-a57e-8a40-e74b-39584b415152@i-love.sakura.ne.jp Link: https://lkml.kernel.org/r/20210731175341.3458608-1-lrizzo@google.com Signed-off-by: Luigi Rizzo <lrizzo@google.com> Cc: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-09-03mm: remove flush_kernel_dcache_pageChristoph Hellwig
flush_kernel_dcache_page is a rather confusing interface that implements a subset of flush_dcache_page by not being able to properly handle page cache mapped pages. The only callers left are in the exec code as all other previous callers were incorrect as they could have dealt with page cache pages. Replace the calls to flush_kernel_dcache_page with calls to flush_dcache_page, which for all architectures does either exactly the same thing, can contains one or more of the following: 1) an optimization to defer the cache flush for page cache pages not mapped into userspace 2) additional flushing for mapped page cache pages if cache aliases are possible Link: https://lkml.kernel.org/r/20210712060928.4161649-7-hch@lst.de Signed-off-by: Christoph Hellwig <hch@lst.de> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Reviewed-by: Ira Weiny <ira.weiny@intel.com> Cc: Alex Shi <alexs@kernel.org> Cc: Geoff Levand <geoff@infradead.org> Cc: Greentime Hu <green.hu@gmail.com> Cc: Guo Ren <guoren@kernel.org> Cc: Helge Deller <deller@gmx.de> Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com> Cc: Nick Hu <nickhu@andestech.com> Cc: Paul Cercueil <paul@crapouillou.net> Cc: Rich Felker <dalias@libc.org> Cc: Russell King <linux@armlinux.org.uk> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de> Cc: Ulf Hansson <ulf.hansson@linaro.org> Cc: Vincent Chen <deanbo422@gmail.com> Cc: Yoshinori Sato <ysato@users.osdn.me> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-09-03kernel/fork: always deny write access to current MM exe_fileDavid Hildenbrand
We want to remove VM_DENYWRITE only currently only used when mapping the executable during exec. During exec, we already deny_write_access() the executable, however, after exec completes the VMAs mapped with VM_DENYWRITE effectively keeps write access denied via deny_write_access(). Let's deny write access when setting or replacing the MM exe_file. With this change, we can remove VM_DENYWRITE for mapping executables. Make set_mm_exe_file() return an error in case deny_write_access() fails; note that this should never happen, because exec code does a deny_write_access() early and keeps write access denied when calling set_mm_exe_file. However, it makes the code easier to read and makes set_mm_exe_file() and replace_mm_exe_file() look more similar. This represents a minor user space visible change: sys_prctl(PR_SET_MM_MAP/EXE_FILE) can now fail if the file is already opened writable. Also, after sys_prctl(PR_SET_MM_MAP/EXE_FILE) the file cannot be opened writable. Note that we can already fail with -EACCES if the file doesn't have execute permissions. Acked-by: "Eric W. Biederman" <ebiederm@xmission.com> Acked-by: Christian König <christian.koenig@amd.com> Signed-off-by: David Hildenbrand <david@redhat.com>
2021-08-23namei: add getname_uflags()Dmitry Kadashev
There are a couple of places where we already open-code the (flags & AT_EMPTY_PATH) check and io_uring will likely add another one in the future. Let's just add a simple helper getname_uflags() that handles this directly and use it. Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Christian Brauner <christian.brauner@ubuntu.com> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Link: https://lore.kernel.org/io-uring/20210415100815.edrn4a7cy26wkowe@wittgenstein/ Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Signed-off-by: Dmitry Kadashev <dkadashev@gmail.com> Acked-by: Christian Brauner <christian.brauner@ubuntu.com> Link: https://lore.kernel.org/r/20210708063447.3556403-7-dkadashev@gmail.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-07-02Merge branch 'akpm' (patches from Andrew)Linus Torvalds
Merge more updates from Andrew Morton: "190 patches. Subsystems affected by this patch series: mm (hugetlb, userfaultfd, vmscan, kconfig, proc, z3fold, zbud, ras, mempolicy, memblock, migration, thp, nommu, kconfig, madvise, memory-hotplug, zswap, zsmalloc, zram, cleanups, kfence, and hmm), procfs, sysctl, misc, core-kernel, lib, lz4, checkpatch, init, kprobes, nilfs2, hfs, signals, exec, kcov, selftests, compress/decompress, and ipc" * emailed patches from Andrew Morton <akpm@linux-foundation.org>: (190 commits) ipc/util.c: use binary search for max_idx ipc/sem.c: use READ_ONCE()/WRITE_ONCE() for use_global_lock ipc: use kmalloc for msg_queue and shmid_kernel ipc sem: use kvmalloc for sem_undo allocation lib/decompressors: remove set but not used variabled 'level' selftests/vm/pkeys: exercise x86 XSAVE init state selftests/vm/pkeys: refill shadow register after implicit kernel write selftests/vm/pkeys: handle negative sys_pkey_alloc() return code selftests/vm/pkeys: fix alloc_random_pkey() to make it really, really random kcov: add __no_sanitize_coverage to fix noinstr for all architectures exec: remove checks in __register_bimfmt() x86: signal: don't do sas_ss_reset() until we are certain that sigframe won't be abandoned hfsplus: report create_date to kstat.btime hfsplus: remove unnecessary oom message nilfs2: remove redundant continue statement in a while-loop kprobes: remove duplicated strong free_insn_page in x86 and s390 init: print out unknown kernel parameters checkpatch: do not complain about positive return values starting with EPOLL checkpatch: improve the indented label test checkpatch: scripts/spdxcheck.py now requires python3 ...
2021-07-01exec: remove checks in __register_bimfmt()Alexey Dobriyan
Delete NULL check, all callers pass valid pointer. Delete ->load_binary check -- failure to provide hook in a custom module will be very noticeable at the very first execve call. Link: https://lkml.kernel.org/r/YK1Gy1qXaLAR+tPl@localhost.localdomain Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-04-30Reimplement RLIMIT_NPROC on top of ucountsAlexey Gladkov
The rlimit counter is tied to uid in the user_namespace. This allows rlimit values to be specified in userns even if they are already globally exceeded by the user. However, the value of the previous user_namespaces cannot be exceeded. To illustrate the impact of rlimits, let's say there is a program that does not fork. Some service-A wants to run this program as user X in multiple containers. Since the program never fork the service wants to set RLIMIT_NPROC=1. service-A \- program (uid=1000, container1, rlimit_nproc=1) \- program (uid=1000, container2, rlimit_nproc=1) The service-A sets RLIMIT_NPROC=1 and runs the program in container1. When the service-A tries to run a program with RLIMIT_NPROC=1 in container2 it fails since user X already has one running process. We cannot use existing inc_ucounts / dec_ucounts because they do not allow us to exceed the maximum for the counter. Some rlimits can be overlimited by root or if the user has the appropriate capability. Changelog v11: * Change inc_rlimit_ucounts() which now returns top value of ucounts. * Drop inc_rlimit_ucounts_and_test() because the return code of inc_rlimit_ucounts() can be checked. Signed-off-by: Alexey Gladkov <legion@kernel.org> Link: https://lkml.kernel.org/r/c5286a8aa16d2d698c222f7532f3d735c82bc6bc.1619094428.git.legion@kernel.org Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2021-04-30Add a reference to ucounts for each credAlexey Gladkov
For RLIMIT_NPROC and some other rlimits the user_struct that holds the global limit is kept alive for the lifetime of a process by keeping it in struct cred. Adding a pointer to ucounts in the struct cred will allow to track RLIMIT_NPROC not only for user in the system, but for user in the user_namespace. Updating ucounts may require memory allocation which may fail. So, we cannot change cred.ucounts in the commit_creds() because this function cannot fail and it should always return 0. For this reason, we modify cred.ucounts before calling the commit_creds(). Changelog v6: * Fix null-ptr-deref in is_ucounts_overlimit() detected by trinity. This error was caused by the fact that cred_alloc_blank() left the ucounts pointer empty. Reported-by: kernel test robot <oliver.sang@intel.com> Signed-off-by: Alexey Gladkov <legion@kernel.org> Link: https://lkml.kernel.org/r/b37aaef28d8b9b0d757e07ba6dd27281bbe39259.1619094428.git.legion@kernel.org Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2021-02-24fs: delete repeated words in commentsRandy Dunlap
Delete duplicate words in fs/*.c. The doubled words that are being dropped are: that, be, the, in, and, for Link: https://lkml.kernel.org/r/20201224052810.25315-1-rdunlap@infradead.org Signed-off-by: Randy Dunlap <rdunlap@infradead.org> Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-02-23Merge tag 'idmapped-mounts-v5.12' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux Pull idmapped mounts from Christian Brauner: "This introduces idmapped mounts which has been in the making for some time. Simply put, different mounts can expose the same file or directory with different ownership. This initial implementation comes with ports for fat, ext4 and with Christoph's port for xfs with more filesystems being actively worked on by independent people and maintainers. Idmapping mounts handle a wide range of long standing use-cases. Here are just a few: - Idmapped mounts make it possible to easily share files between multiple users or multiple machines especially in complex scenarios. For example, idmapped mounts will be used in the implementation of portable home directories in systemd-homed.service(8) where they allow users to move their home directory to an external storage device and use it on multiple computers where they are assigned different uids and gids. This effectively makes it possible to assign random uids and gids at login time. - It is possible to share files from the host with unprivileged containers without having to change ownership permanently through chown(2). - It is possible to idmap a container's rootfs and without having to mangle every file. For example, Chromebooks use it to share the user's Download folder with their unprivileged containers in their Linux subsystem. - It is possible to share files between containers with non-overlapping idmappings. - Filesystem that lack a proper concept of ownership such as fat can use idmapped mounts to implement discretionary access (DAC) permission checking. - They allow users to efficiently changing ownership on a per-mount basis without having to (recursively) chown(2) all files. In contrast to chown (2) changing ownership of large sets of files is instantenous with idmapped mounts. This is especially useful when ownership of a whole root filesystem of a virtual machine or container is changed. With idmapped mounts a single syscall mount_setattr syscall will be sufficient to change the ownership of all files. - Idmapped mounts always take the current ownership into account as idmappings specify what a given uid or gid is supposed to be mapped to. This contrasts with the chown(2) syscall which cannot by itself take the current ownership of the files it changes into account. It simply changes the ownership to the specified uid and gid. This is especially problematic when recursively chown(2)ing a large set of files which is commong with the aforementioned portable home directory and container and vm scenario. - Idmapped mounts allow to change ownership locally, restricting it to specific mounts, and temporarily as the ownership changes only apply as long as the mount exists. Several userspace projects have either already put up patches and pull-requests for this feature or will do so should you decide to pull this: - systemd: In a wide variety of scenarios but especially right away in their implementation of portable home directories. https://systemd.io/HOME_DIRECTORY/ - container runtimes: containerd, runC, LXD:To share data between host and unprivileged containers, unprivileged and privileged containers, etc. The pull request for idmapped mounts support in containerd, the default Kubernetes runtime is already up for quite a while now: https://github.com/containerd/containerd/pull/4734 - The virtio-fs developers and several users have expressed interest in using this feature with virtual machines once virtio-fs is ported. - ChromeOS: Sharing host-directories with unprivileged containers. I've tightly synced with all those projects and all of those listed here have also expressed their need/desire for this feature on the mailing list. For more info on how people use this there's a bunch of talks about this too. Here's just two recent ones: https://www.cncf.io/wp-content/uploads/2020/12/Rootless-Containers-in-Gitpod.pdf https://fosdem.org/2021/schedule/event/containers_idmap/ This comes with an extensive xfstests suite covering both ext4 and xfs: https://git.kernel.org/brauner/xfstests-dev/h/idmapped_mounts It covers truncation, creation, opening, xattrs, vfscaps, setid execution, setgid inheritance and more both with idmapped and non-idmapped mounts. It already helped to discover an unrelated xfs setgid inheritance bug which has since been fixed in mainline. It will be sent for inclusion with the xfstests project should you decide to merge this. In order to support per-mount idmappings vfsmounts are marked with user namespaces. The idmapping of the user namespace will be used to map the ids of vfs objects when they are accessed through that mount. By default all vfsmounts are marked with the initial user namespace. The initial user namespace is used to indicate that a mount is not idmapped. All operations behave as before and this is verified in the testsuite. Based on prior discussions we want to attach the whole user namespace and not just a dedicated idmapping struct. This allows us to reuse all the helpers that already exist for dealing with idmappings instead of introducing a whole new range of helpers. In addition, if we decide in the future that we are confident enough to enable unprivileged users to setup idmapped mounts the permission checking can take into account whether the caller is privileged in the user namespace the mount is currently marked with. The user namespace the mount will be marked with can be specified by passing a file descriptor refering to the user namespace as an argument to the new mount_setattr() syscall together with the new MOUNT_ATTR_IDMAP flag. The system call follows the openat2() pattern of extensibility. The following conditions must be met in order to create an idmapped mount: - The caller must currently have the CAP_SYS_ADMIN capability in the user namespace the underlying filesystem has been mounted in. - The underlying filesystem must support idmapped mounts. - The mount must not already be idmapped. This also implies that the idmapping of a mount cannot be altered once it has been idmapped. - The mount must be a detached/anonymous mount, i.e. it must have been created by calling open_tree() with the OPEN_TREE_CLONE flag and it must not already have been visible in the filesystem. The last two points guarantee easier semantics for userspace and the kernel and make the implementation significantly simpler. By default vfsmounts are marked with the initial user namespace and no behavioral or performance changes are observed. The manpage with a detailed description can be found here: https://git.kernel.org/brauner/man-pages/c/1d7b902e2875a1ff342e036a9f866a995640aea8 In order to support idmapped mounts, filesystems need to be changed and mark themselves with the FS_ALLOW_IDMAP flag in fs_flags. The patches to convert individual filesystem are not very large or complicated overall as can be seen from the included fat, ext4, and xfs ports. Patches for other filesystems are actively worked on and will be sent out separately. The xfstestsuite can be used to verify that port has been done correctly. The mount_setattr() syscall is motivated independent of the idmapped mounts patches and it's been around since July 2019. One of the most valuable features of the new mount api is the ability to perform mounts based on file descriptors only. Together with the lookup restrictions available in the openat2() RESOLVE_* flag namespace which we added in v5.6 this is the first time we are close to hardened and race-free (e.g. symlinks) mounting and path resolution. While userspace has started porting to the new mount api to mount proper filesystems and create new bind-mounts it is currently not possible to change mount options of an already existing bind mount in the new mount api since the mount_setattr() syscall is missing. With the addition of the mount_setattr() syscall we remove this last restriction and userspace can now fully port to the new mount api, covering every use-case the old mount api could. We also add the crucial ability to recursively change mount options for a whole mount tree, both removing and adding mount options at the same time. This syscall has been requested multiple times by various people and projects. There is a simple tool available at https://github.com/brauner/mount-idmapped that allows to create idmapped mounts so people can play with this patch series. I'll add support for the regular mount binary should you decide to pull this in the following weeks: Here's an example to a simple idmapped mount of another user's home directory: u1001@f2-vm:/$ sudo ./mount --idmap both:1000:1001:1 /home/ubuntu/ /mnt u1001@f2-vm:/$ ls -al /home/ubuntu/ total 28 drwxr-xr-x 2 ubuntu ubuntu 4096 Oct 28 22:07 . drwxr-xr-x 4 root root 4096 Oct 28 04:00 .. -rw------- 1 ubuntu ubuntu 3154 Oct 28 22:12 .bash_history -rw-r--r-- 1 ubuntu ubuntu 220 Feb 25 2020 .bash_logout -rw-r--r-- 1 ubuntu ubuntu 3771 Feb 25 2020 .bashrc -rw-r--r-- 1 ubuntu ubuntu 807 Feb 25 2020 .profile -rw-r--r-- 1 ubuntu ubuntu 0 Oct 16 16:11 .sudo_as_admin_successful -rw------- 1 ubuntu ubuntu 1144 Oct 28 00:43 .viminfo u1001@f2-vm:/$ ls -al /mnt/ total 28 drwxr-xr-x 2 u1001 u1001 4096 Oct 28 22:07 . drwxr-xr-x 29 root root 4096 Oct 28 22:01 .. -rw------- 1 u1001 u1001 3154 Oct 28 22:12 .bash_history -rw-r--r-- 1 u1001 u1001 220 Feb 25 2020 .bash_logout -rw-r--r-- 1 u1001 u1001 3771 Feb 25 2020 .bashrc -rw-r--r-- 1 u1001 u1001 807 Feb 25 2020 .profile -rw-r--r-- 1 u1001 u1001 0 Oct 16 16:11 .sudo_as_admin_successful -rw------- 1 u1001 u1001 1144 Oct 28 00:43 .viminfo u1001@f2-vm:/$ touch /mnt/my-file u1001@f2-vm:/$ setfacl -m u:1001:rwx /mnt/my-file u1001@f2-vm:/$ sudo setcap -n 1001 cap_net_raw+ep /mnt/my-file u1001@f2-vm:/$ ls -al /mnt/my-file -rw-rwxr--+ 1 u1001 u1001 0 Oct 28 22:14 /mnt/my-file u1001@f2-vm:/$ ls -al /home/ubuntu/my-file -rw-rwxr--+ 1 ubuntu ubuntu 0 Oct 28 22:14 /home/ubuntu/my-file u1001@f2-vm:/$ getfacl /mnt/my-file getfacl: Removing leading '/' from absolute path names # file: mnt/my-file # owner: u1001 # group: u1001 user::rw- user:u1001:rwx group::rw- mask::rwx other::r-- u1001@f2-vm:/$ getfacl /home/ubuntu/my-file getfacl: Removing leading '/' from absolute path names # file: home/ubuntu/my-file # owner: ubuntu # group: ubuntu user::rw- user:ubuntu:rwx group::rw- mask::rwx other::r--" * tag 'idmapped-mounts-v5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux: (41 commits) xfs: remove the possibly unused mp variable in xfs_file_compat_ioctl xfs: support idmapped mounts ext4: support idmapped mounts fat: handle idmapped mounts tests: add mount_setattr() selftests fs: introduce MOUNT_ATTR_IDMAP fs: add mount_setattr() fs: add attr_flags_to_mnt_flags helper fs: split out functions to hold writers namespace: only take read lock in do_reconfigure_mnt() mount: make {lock,unlock}_mount_hash() static namespace: take lock_mount_hash() directly when changing flags nfs: do not export idmapped mounts overlayfs: do not mount on top of idmapped mounts ecryptfs: do not mount on top of idmapped mounts ima: handle idmapped mounts apparmor: handle idmapped mounts fs: make helpers idmap mount aware exec: handle idmapped mounts would_dump: handle idmapped mounts ...
2021-01-29tlb: mmu_gather: Remove start/end arguments from tlb_gather_mmu()Will Deacon
The 'start' and 'end' arguments to tlb_gather_mmu() are no longer needed now that there is a separate function for 'fullmm' flushing. Remove the unused arguments and update all callers. Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Will Deacon <will@kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Yu Zhao <yuzhao@google.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Link: https://lore.kernel.org/r/CAHk-=wjQWa14_4UpfDf=fiineNP+RH74kZeDMo_f1D35xNzq9w@mail.gmail.com
2021-01-29tlb: mmu_gather: Remove unused start/end arguments from tlb_finish_mmu()Will Deacon
Since commit 7a30df49f63a ("mm: mmu_gather: remove __tlb_reset_range() for force flush"), the 'start' and 'end' arguments to tlb_finish_mmu() are no longer used, since we flush the whole mm in case of a nested invalidation. Remove the unused arguments and update all callers. Signed-off-by: Will Deacon <will@kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Yu Zhao <yuzhao@google.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Link: https://lkml.kernel.org/r/20210127235347.1402-3-will@kernel.org
2021-01-24exec: handle idmapped mountsChristian Brauner
When executing a setuid binary the kernel will verify in bprm_fill_uid() that the inode has a mapping in the caller's user namespace before setting the callers uid and gid. Let bprm_fill_uid() handle idmapped mounts. If the inode is accessed through an idmapped mount it is mapped according to the mount's user namespace. Afterwards the checks are identical to non-idmapped mounts. If the initial user namespace is passed nothing changes so non-idmapped mounts will see identical behavior as before. Link: https://lore.kernel.org/r/20210121131959.646623-24-christian.brauner@ubuntu.com Cc: Christoph Hellwig <hch@lst.de> Cc: David Howells <dhowells@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: linux-fsdevel@vger.kernel.org Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: James Morris <jamorris@linux.microsoft.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>