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authorOleg Nesterov <oleg@redhat.com>2012-03-23 15:02:50 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-03-23 16:58:42 -0700
commit1cc684ab75123efe7ff446eb821d44375ba8fa30 (patch)
tree165069093fc048b979ed38e537b19febdc7889d3
parent3e63a93b987685f02421e18b2aa452d20553a88b (diff)
kmod: make __request_module() killable
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>
-rw-r--r--kernel/kmod.c26
1 files changed, 24 insertions, 2 deletions
diff --git a/kernel/kmod.c b/kernel/kmod.c
index 56a29e812ff..957a7aab8eb 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -60,6 +60,12 @@ static DECLARE_RWSEM(umhelper_sem);
*/
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[] = {
@@ -69,10 +75,26 @@ 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;
}
/**