| Date | Mon, 04 Mar 2013 03:39:35 +0000 | From | Ben Hutchings <> | Subject | [ 148/153] kmod: make __request_module() killable |
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3.2-stable review patch. If anyone has any objections, please let me know.
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From: Oleg Nesterov <oleg@redhat.com>
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> --- kernel/kmod.c | 26 ++++++++++++++++++++++++-- 1 file changed, 24 insertions(+), 2 deletions(-)
--- 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_na 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; } /**
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