From d6b2123802d2b7eee8c62cd0ebd73e8636cbb068 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Wed, 10 Oct 2012 19:57:26 -0400 Subject: make sure that we always have a return path from kernel_execve() The only place where kernel_execve() is called without a way to return to the caller of kernel_thread() callback is kernel_post(). Reorganize kernel_init()/kernel_post() - instead of the former calling the latter in the end (and getting freed by it), have the latter *begin* with calling the former (and turn the latter into kernel_thread() callback, of course). Signed-off-by: Al Viro --- init/main.c | 13 +++++-------- 1 file changed, 5 insertions(+), 8 deletions(-) (limited to 'init/main.c') diff --git a/init/main.c b/init/main.c index b28673087ac0..a490ffecb7b9 100644 --- a/init/main.c +++ b/init/main.c @@ -794,11 +794,11 @@ static void run_init_process(const char *init_filename) kernel_execve(init_filename, argv_init, envp_init); } -/* This is a non __init function. Force it to be noinline otherwise gcc - * makes it inline to init() and it becomes part of init.text section - */ -static noinline int init_post(void) +static void __init kernel_init_freeable(void); + +static int __ref kernel_init(void *unused) { + kernel_init_freeable(); /* need to finish all async __init code before freeing the memory */ async_synchronize_full(); free_initmem(); @@ -835,7 +835,7 @@ static noinline int init_post(void) "See Linux Documentation/init.txt for guidance."); } -static int __init kernel_init(void * unused) +static void __init kernel_init_freeable(void) { /* * Wait until kthreadd is all set-up. @@ -890,7 +890,4 @@ static int __init kernel_init(void * unused) * we're essentially up and running. Get rid of the * initmem segments and start the user-mode stuff.. */ - - init_post(); - return 0; } -- cgit v1.2.3-58-ga151 From a74fb73c12398b250fdc5e333a11e15a9e3a84fc Mon Sep 17 00:00:00 2001 From: Al Viro Date: Wed, 10 Oct 2012 21:28:25 -0400 Subject: infrastructure for saner ret_from_kernel_thread semantics * allow kernel_execve() leave the actual return to userland to caller (selected by CONFIG_GENERIC_KERNEL_EXECVE). Callers updated accordingly. * architecture that does select GENERIC_KERNEL_EXECVE in its Kconfig should have its ret_from_kernel_thread() do this: call schedule_tail call the callback left for it by copy_thread(); if it ever returns, that's because it has just done successful kernel_execve() jump to return from syscall IOW, its only difference from ret_from_fork() is that it does call the callback. * such an architecture should also get rid of ret_from_kernel_execve() and __ARCH_WANT_KERNEL_EXECVE This is the last part of infrastructure patches in that area - from that point on work on different architectures can live independently. Signed-off-by: Al Viro --- arch/Kconfig | 3 +++ include/linux/syscalls.h | 8 ++++++++ init/main.c | 20 ++++++++++++-------- kernel/kmod.c | 3 +++ kernel/kthread.c | 1 + 5 files changed, 27 insertions(+), 8 deletions(-) (limited to 'init/main.c') diff --git a/arch/Kconfig b/arch/Kconfig index d397e11d167d..d27efb9bfafd 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -261,6 +261,9 @@ config ARCH_WANT_OLD_COMPAT_IPC config GENERIC_KERNEL_THREAD bool +config GENERIC_KERNEL_EXECVE + bool + config HAVE_ARCH_SECCOMP_FILTER bool help diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 19439c75c5b2..727f0cd73921 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -827,7 +827,15 @@ asmlinkage long sys_fanotify_mark(int fanotify_fd, unsigned int flags, const char __user *pathname); asmlinkage long sys_syncfs(int fd); +#ifndef CONFIG_GENERIC_KERNEL_EXECVE int kernel_execve(const char *filename, const char *const argv[], const char *const envp[]); +#else +#define kernel_execve(filename, argv, envp) \ + do_execve(filename, \ + (const char __user *const __user *)argv, \ + (const char __user *const __user *)envp, \ + current_pt_regs()) +#endif asmlinkage long sys_perf_event_open( diff --git a/init/main.c b/init/main.c index a490ffecb7b9..02df2ddc5f83 100644 --- a/init/main.c +++ b/init/main.c @@ -69,6 +69,7 @@ #include #include #include +#include #include #include @@ -788,10 +789,10 @@ static void __init do_pre_smp_initcalls(void) do_one_initcall(*fn); } -static void run_init_process(const char *init_filename) +static int run_init_process(const char *init_filename) { argv_init[0] = init_filename; - kernel_execve(init_filename, argv_init, envp_init); + return kernel_execve(init_filename, argv_init, envp_init); } static void __init kernel_init_freeable(void); @@ -810,7 +811,8 @@ static int __ref kernel_init(void *unused) flush_delayed_fput(); if (ramdisk_execute_command) { - run_init_process(ramdisk_execute_command); + if (!run_init_process(ramdisk_execute_command)) + return 0; printk(KERN_WARNING "Failed to execute %s\n", ramdisk_execute_command); } @@ -822,14 +824,16 @@ static int __ref kernel_init(void *unused) * trying to recover a really broken machine. */ if (execute_command) { - run_init_process(execute_command); + if (!run_init_process(execute_command)) + return 0; printk(KERN_WARNING "Failed to execute %s. Attempting " "defaults...\n", execute_command); } - run_init_process("/sbin/init"); - run_init_process("/etc/init"); - run_init_process("/bin/init"); - run_init_process("/bin/sh"); + if (!run_init_process("/sbin/init") || + !run_init_process("/etc/init") || + !run_init_process("/bin/init") || + !run_init_process("/bin/sh")) + return 0; panic("No init found. Try passing init= option to kernel. " "See Linux Documentation/init.txt for guidance."); diff --git a/kernel/kmod.c b/kernel/kmod.c index b6e5ca9c758a..1c317e386831 100644 --- a/kernel/kmod.c +++ b/kernel/kmod.c @@ -37,6 +37,7 @@ #include #include #include +#include #include #include @@ -221,6 +222,8 @@ static int ____call_usermodehelper(void *data) retval = kernel_execve(sub_info->path, (const char *const *)sub_info->argv, (const char *const *)sub_info->envp); + if (!retval) + return 0; /* Exec failed? */ fail: diff --git a/kernel/kthread.c b/kernel/kthread.c index b579af57ea10..7ba65c1aa6b3 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -16,6 +16,7 @@ #include #include #include +#include #include static DEFINE_SPINLOCK(kthread_create_lock); -- cgit v1.2.3-58-ga151