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| author | Oleg Nesterov <oleg@redhat.com> | 2012-03-23 15:02:50 -0700 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2013-03-06 03:24:28 +0000 |
| commit | d0820f8020fa87d9e0433b062fca2b7206e0cd11 (patch) | |
| tree | daf7f76eb17112151d4883ce57103877e2441532 | |
| parent | 95b467ca30d2e56c08fbe541a02318470457cca7 (diff) | |
| download | lwn-d0820f8020fa87d9e0433b062fca2b7206e0cd11.tar.gz lwn-d0820f8020fa87d9e0433b062fca2b7206e0cd11.zip | |
kmod: make __request_module() killable
commit 1cc684ab75123efe7ff446eb821d44375ba8fa30 upstream.
As Tetsuo Handa pointed out, request_module() can stress the system
while the oom-killed caller sleeps in TASK_UNINTERRUPTIBLE.
The task T uses "almost all" memory, then it does something which
triggers request_module(). Say, it can simply call sys_socket(). This
in turn needs more memory and leads to OOM. oom-killer correctly
chooses T and kills it, but this can't help because it sleeps in
TASK_UNINTERRUPTIBLE and after that oom-killer becomes "disabled" by the
TIF_MEMDIE task T.
Make __request_module() killable. The only necessary change is that
call_modprobe() should kmalloc argv and module_name, they can't live in
the stack if we use UMH_KILLABLE. This memory is freed via
call_usermodehelper_freeinfo()->cleanup.
Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Tejun Heo <tj@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
| -rw-r--r-- | kernel/kmod.c | 26 |
1 files changed, 24 insertions, 2 deletions
diff --git a/kernel/kmod.c b/kernel/kmod.c index 135041fcef5e..d6fe08a1707c 100644 --- a/kernel/kmod.c +++ b/kernel/kmod.c @@ -58,6 +58,12 @@ static DEFINE_SPINLOCK(umh_sysctl_lock); */ char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe"; +static void free_modprobe_argv(struct subprocess_info *info) +{ + kfree(info->argv[3]); /* check call_modprobe() */ + kfree(info->argv); +} + static int call_modprobe(char *module_name, int wait) { static char *envp[] = { @@ -67,10 +73,26 @@ static int call_modprobe(char *module_name, int wait) NULL }; - char *argv[] = { modprobe_path, "-q", "--", module_name, NULL }; + char **argv = kmalloc(sizeof(char *[5]), GFP_KERNEL); + if (!argv) + goto out; + + module_name = kstrdup(module_name, GFP_KERNEL); + if (!module_name) + goto free_argv; + + argv[0] = modprobe_path; + argv[1] = "-q"; + argv[2] = "--"; + argv[3] = module_name; /* check free_modprobe_argv() */ + argv[4] = NULL; return call_usermodehelper_fns(modprobe_path, argv, envp, - wait, NULL, NULL, NULL); + wait | UMH_KILLABLE, NULL, free_modprobe_argv, NULL); +free_argv: + kfree(argv); +out: + return -ENOMEM; } /** |