3.2-stable review patch. If anyone has any objections, please let me know.
------------------
From: Oleg Nesterov <oleg@xxxxxxxxxx>
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@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
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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