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It is easy to trigger this with CONFIG_HARDENED_USERCOPY_PAGESPAN=y,
usercopy: Kernel memory overwrite attempt detected to spans multiple pages (offset 0, size 23)!
kernel BUG at mm/usercopy.c:102!
For example,
print_worker_info
char name[WQ_NAME_LEN] = { };
char desc[WORKER_DESC_LEN] = { };
probe_kernel_read(name, wq->name, sizeof(name) - 1);
probe_kernel_read(desc, worker->desc, sizeof(desc) - 1);
__copy_from_user_inatomic
check_object_size
check_heap_object
check_page_span
This is because on-stack variables could cross PAGE_SIZE boundary, and
failed this check,
if (likely(((unsigned long)ptr & (unsigned long)PAGE_MASK) ==
((unsigned long)end & (unsigned long)PAGE_MASK)))
ptr = FFFF889007D7EFF8
end = FFFF889007D7F00E
Hence, fix it by checking if it is a stack object first.
[keescook@chromium.org: improve comments after reorder]
Link: http://lkml.kernel.org/r/20190103165151.GA32845@beast
Link: http://lkml.kernel.org/r/20181231030254.99441-1-cai@lca.pw
Signed-off-by: Qian Cai <cai@lca.pw>
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Enabling HARDENED_USERCOPY may cause measurable regressions in networking
performance: up to 8% under UDP flood.
I ran a small packet UDP flood using pktgen vs. a host b2b connected. On
the receiver side the UDP packets are processed by a simple user space
process that just reads and drops them:
https://github.com/netoptimizer/network-testing/blob/master/src/udp_sink.c
Not very useful from a functional PoV, but it helps to pin-point
bottlenecks in the networking stack.
When running a kernel with CONFIG_HARDENED_USERCOPY=y, I see a 5-8%
regression in the receive tput, compared to the same kernel without this
option enabled.
With CONFIG_HARDENED_USERCOPY=y, perf shows ~6% of CPU time spent
cumulatively in __check_object_size (~4%) and __virt_addr_valid (~2%).
The call-chain is:
__GI___libc_recvfrom
entry_SYSCALL_64_after_hwframe
do_syscall_64
__x64_sys_recvfrom
__sys_recvfrom
inet_recvmsg
udp_recvmsg
__check_object_size
udp_recvmsg() actually calls copy_to_iter() (inlined) and the latters
calls check_copy_size() (again, inlined).
A generic distro may want to enable HARDENED_USERCOPY in their default
kernel config, but at the same time, such distro may want to be able to
avoid the performance penalties in with the default configuration and
disable the stricter check on a per-boot basis.
This change adds a boot parameter that conditionally disables
HARDENED_USERCOPY via "hardened_usercopy=off".
Signed-off-by: Chris von Recklinghausen <crecklin@redhat.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
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This patch adds checking of usercopy cache whitelisting, and is modified
from Brad Spengler/PaX Team's PAX_USERCOPY whitelisting code in the
last public patch of grsecurity/PaX based on my understanding of the
code. Changes or omissions from the original code are mine and don't
reflect the original grsecurity/PaX code.
The SLAB and SLUB allocators are modified to WARN() on all copy operations
in which the kernel heap memory being modified falls outside of the cache's
defined usercopy region.
Based on an earlier patch from David Windsor.
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: linux-mm@kvack.org
Cc: linux-xfs@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
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This refactors the hardened usercopy code so that failure reporting can
happen within the checking functions instead of at the top level. This
simplifies the return value handling and allows more details and offsets
to be included in the report. Having the offset can be much more helpful
in understanding hardened usercopy bugs.
Signed-off-by: Kees Cook <keescook@chromium.org>
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In preparation for refactoring the usercopy checks to pass offset to
the hardened usercopy report, this renames report_usercopy() to the
more accurate usercopy_abort(), marks it as noreturn because it is,
adds a hopefully helpful comment for anyone investigating such reports,
makes the function available to the slab allocators, and adds new "detail"
and "offset" arguments.
Signed-off-by: Kees Cook <keescook@chromium.org>
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Using %p was already mostly useless in the usercopy overflow reports,
so this removes it entirely to avoid confusion now that %p-hashing
is enabled.
Fixes: ad67b74d2469d9b8 ("printk: hash addresses printed with %p")
Signed-off-by: Kees Cook <keescook@chromium.org>
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Previously virt_addr_valid() was insufficient to validate if virt_to_page()
could be called on an address on arm64. This has since been fixed up so
there is no need for the extra check. Drop it.
Signed-off-by: Laura Abbott <labbott@redhat.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
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This patch moves the arch_within_stack_frames() return value enum up in
the header files so that per-architecture implementations can reuse the
same return values.
Signed-off-by: Sahara <keun-o.park@darkmatter.ae>
Signed-off-by: James Morse <james.morse@arm.com>
[kees: adjusted naming and commit log]
Signed-off-by: Kees Cook <keescook@chromium.org>
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<linux/sched/task.h>
We are going to split <linux/sched/task.h> out of <linux/sched.h>, which
will have to be picked up from other headers and a couple of .c files.
Create a trivial placeholder <linux/sched/task.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.
Include the new header in the files that are going to need it.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Add #include <linux/cred.h> dependencies to all .c files rely on sched.h
doing that for them.
Note that even if the count where we need to add extra headers seems high,
it's still a net win, because <linux/sched.h> is included in over
2,200 files ...
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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The usercopy checking code currently calls __va(__pa(...)) to check for
aliases on symbols. Switch to using lm_alias instead.
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Laura Abbott <labbott@redhat.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
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While running a compile on arm64, I hit a memory exposure
usercopy: kernel memory exposure attempt detected from fffffc0000f3b1a8 (buffer_head) (1 bytes)
------------[ cut here ]------------
kernel BUG at mm/usercopy.c:75!
Internal error: Oops - BUG: 0 [#1] SMP
Modules linked in: ip6t_rpfilter ip6t_REJECT
nf_reject_ipv6 xt_conntrack ip_set nfnetlink ebtable_broute bridge stp
llc ebtable_nat ip6table_security ip6table_raw ip6table_nat
nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 ip6table_mangle
iptable_security iptable_raw iptable_nat nf_conntrack_ipv4
nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack iptable_mangle
ebtable_filter ebtables ip6table_filter ip6_tables vfat fat xgene_edac
xgene_enet edac_core i2c_xgene_slimpro i2c_core at803x realtek xgene_dma
mdio_xgene gpio_dwapb gpio_xgene_sb xgene_rng mailbox_xgene_slimpro nfsd
auth_rpcgss nfs_acl lockd grace sunrpc xfs libcrc32c sdhci_of_arasan
sdhci_pltfm sdhci mmc_core xhci_plat_hcd gpio_keys
CPU: 0 PID: 19744 Comm: updatedb Tainted: G W 4.8.0-rc3-threadinfo+ #1
Hardware name: AppliedMicro X-Gene Mustang Board/X-Gene Mustang Board, BIOS 3.06.12 Aug 12 2016
task: fffffe03df944c00 task.stack: fffffe00d128c000
PC is at __check_object_size+0x70/0x3f0
LR is at __check_object_size+0x70/0x3f0
...
[<fffffc00082b4280>] __check_object_size+0x70/0x3f0
[<fffffc00082cdc30>] filldir64+0x158/0x1a0
[<fffffc0000f327e8>] __fat_readdir+0x4a0/0x558 [fat]
[<fffffc0000f328d4>] fat_readdir+0x34/0x40 [fat]
[<fffffc00082cd8f8>] iterate_dir+0x190/0x1e0
[<fffffc00082cde58>] SyS_getdents64+0x88/0x120
[<fffffc0008082c70>] el0_svc_naked+0x24/0x28
fffffc0000f3b1a8 is a module address. Modules may have compiled in
strings which could get copied to userspace. In this instance, it
looks like "." which matches with a size of 1 byte. Extend the
is_vmalloc_addr check to be is_vmalloc_or_module_addr to cover
all possible cases.
Signed-off-by: Laura Abbott <labbott@redhat.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
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A custom allocator without __GFP_COMP that copies to userspace has been
found in vmw_execbuf_process[1], so this disables the page-span checker
by placing it behind a CONFIG for future work where such things can be
tracked down later.
[1] https://bugzilla.redhat.com/show_bug.cgi?id=1373326
Reported-by: Vinson Lee <vlee@freedesktop.org>
Fixes: f5509cc18daa ("mm: Hardened usercopy")
Signed-off-by: Kees Cook <keescook@chromium.org>
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When running with a local patch which moves the '_stext' symbol to the
very beginning of the kernel text area, I got the following panic with
CONFIG_HARDENED_USERCOPY:
usercopy: kernel memory exposure attempt detected from ffff88103dfff000 (<linear kernel text>) (4096 bytes)
------------[ cut here ]------------
kernel BUG at mm/usercopy.c:79!
invalid opcode: 0000 [#1] SMP
...
CPU: 0 PID: 4800 Comm: cp Not tainted 4.8.0-rc3.after+ #1
Hardware name: Dell Inc. PowerEdge R720/0X3D66, BIOS 2.5.4 01/22/2016
task: ffff880817444140 task.stack: ffff880816274000
RIP: 0010:[<ffffffff8121c796>] __check_object_size+0x76/0x413
RSP: 0018:ffff880816277c40 EFLAGS: 00010246
RAX: 000000000000006b RBX: ffff88103dfff000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffff88081f80dfa8 RDI: ffff88081f80dfa8
RBP: ffff880816277c90 R08: 000000000000054c R09: 0000000000000000
R10: 0000000000000005 R11: 0000000000000006 R12: 0000000000001000
R13: ffff88103e000000 R14: ffff88103dffffff R15: 0000000000000001
FS: 00007fb9d1750800(0000) GS:ffff88081f800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000021d2000 CR3: 000000081a08f000 CR4: 00000000001406f0
Stack:
ffff880816277cc8 0000000000010000 000000043de07000 0000000000000000
0000000000001000 ffff880816277e60 0000000000001000 ffff880816277e28
000000000000c000 0000000000001000 ffff880816277ce8 ffffffff8136c3a6
Call Trace:
[<ffffffff8136c3a6>] copy_page_to_iter_iovec+0xa6/0x1c0
[<ffffffff8136e766>] copy_page_to_iter+0x16/0x90
[<ffffffff811970e3>] generic_file_read_iter+0x3e3/0x7c0
[<ffffffffa06a738d>] ? xfs_file_buffered_aio_write+0xad/0x260 [xfs]
[<ffffffff816e6262>] ? down_read+0x12/0x40
[<ffffffffa06a61b1>] xfs_file_buffered_aio_read+0x51/0xc0 [xfs]
[<ffffffffa06a6692>] xfs_file_read_iter+0x62/0xb0 [xfs]
[<ffffffff812224cf>] __vfs_read+0xdf/0x130
[<ffffffff81222c9e>] vfs_read+0x8e/0x140
[<ffffffff81224195>] SyS_read+0x55/0xc0
[<ffffffff81003a47>] do_syscall_64+0x67/0x160
[<ffffffff816e8421>] entry_SYSCALL64_slow_path+0x25/0x25
RIP: 0033:[<00007fb9d0c33c00>] 0x7fb9d0c33c00
RSP: 002b:00007ffc9c262f28 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: fffffffffff8ffff RCX: 00007fb9d0c33c00
RDX: 0000000000010000 RSI: 00000000021c3000 RDI: 0000000000000004
RBP: 00000000021c3000 R08: 0000000000000000 R09: 00007ffc9c264d6c
R10: 00007ffc9c262c50 R11: 0000000000000246 R12: 0000000000010000
R13: 00007ffc9c2630b0 R14: 0000000000000004 R15: 0000000000010000
Code: 81 48 0f 44 d0 48 c7 c6 90 4d a3 81 48 c7 c0 bb b3 a2 81 48 0f 44 f0 4d 89 e1 48 89 d9 48 c7 c7 68 16 a3 81 31 c0 e8 f4 57 f7 ff <0f> 0b 48 8d 90 00 40 00 00 48 39 d3 0f 83 22 01 00 00 48 39 c3
RIP [<ffffffff8121c796>] __check_object_size+0x76/0x413
RSP <ffff880816277c40>
The checked object's range [ffff88103dfff000, ffff88103e000000) is
valid, so there shouldn't have been a BUG. The hardened usercopy code
got confused because the range's ending address is the same as the
kernel's text starting address at 0xffff88103e000000. The overlap check
is slightly off.
Fixes: f5509cc18daa ("mm: Hardened usercopy")
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
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check_bogus_address() checked for pointer overflow using this expression,
where 'ptr' has type 'const void *':
ptr + n < ptr
Since pointer wraparound is undefined behavior, gcc at -O2 by default
treats it like the following, which would not behave as intended:
(long)n < 0
Fortunately, this doesn't currently happen for kernel code because kernel
code is compiled with -fno-strict-overflow. But the expression should be
fixed anyway to use well-defined integer arithmetic, since it could be
treated differently by different compilers in the future or could be
reported by tools checking for undefined behavior.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
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This is the start of porting PAX_USERCOPY into the mainline kernel. This
is the first set of features, controlled by CONFIG_HARDENED_USERCOPY. The
work is based on code by PaX Team and Brad Spengler, and an earlier port
from Casey Schaufler. Additional non-slab page tests are from Rik van Riel.
This patch contains the logic for validating several conditions when
performing copy_to_user() and copy_from_user() on the kernel object
being copied to/from:
- address range doesn't wrap around
- address range isn't NULL or zero-allocated (with a non-zero copy size)
- if on the slab allocator:
- object size must be less than or equal to copy size (when check is
implemented in the allocator, which appear in subsequent patches)
- otherwise, object must not span page allocations (excepting Reserved
and CMA ranges)
- if on the stack
- object must not extend before/after the current process stack
- object must be contained by a valid stack frame (when there is
arch/build support for identifying stack frames)
- object must not overlap with kernel text
Signed-off-by: Kees Cook <keescook@chromium.org>
Tested-by: Valdis Kletnieks <valdis.kletnieks@vt.edu>
Tested-by: Michael Ellerman <mpe@ellerman.id.au>
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