The patch titled
kmod: fix race in usermodehelper code
has been added to the -mm tree. Its filename is
kmod-fix-race-in-usermodehelper-code.patch
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------------------------------------------------------
Subject: kmod: fix race in usermodehelper code
From: Neil Horman <nhorman@xxxxxxxxxxxxx>
The user mode helper code has a race in it. call_usermodehelper_exec()
takes an allocated subprocess_info structure, which it passes to a
workqueue, and then passes it to a kernel thread which it creates, after
which it calls complete to signal to the caller of
call_usermodehelper_exec() that it can free the subprocess_info struct.
But since we use that structure in the created thread, we can't call
complete from __call_usermodehelper(), which is where we create the kernel
thread. We need to call complete() from within the kernel thread and then
not use subprocess_info afterward in the case of UMH_WAIT_EXEC. Tested
successfully by me.
Signed-off-by: Neil Horman <nhorman@xxxxxxxxxxxxx>
Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/kmod.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)
diff -puN kernel/kmod.c~kmod-fix-race-in-usermodehelper-code kernel/kmod.c
--- a/kernel/kmod.c~kmod-fix-race-in-usermodehelper-code
+++ a/kernel/kmod.c
@@ -136,6 +136,7 @@ struct subprocess_info {
static int ____call_usermodehelper(void *data)
{
struct subprocess_info *sub_info = data;
+ enum umh_wait wait = sub_info->wait;
int retval;
BUG_ON(atomic_read(&sub_info->cred->usage) != 1);
@@ -177,10 +178,14 @@ static int ____call_usermodehelper(void
*/
set_user_nice(current, 0);
+ if (wait == UMH_WAIT_EXEC)
+ complete(sub_info->complete);
+
retval = kernel_execve(sub_info->path, sub_info->argv, sub_info->envp);
/* Exec failed? */
- sub_info->retval = retval;
+ if (wait != UMH_WAIT_EXEC)
+ sub_info->retval = retval;
do_exit(0);
}
@@ -259,16 +264,14 @@ static void __call_usermodehelper(struct
switch (wait) {
case UMH_NO_WAIT:
+ case UMH_WAIT_EXEC:
break;
case UMH_WAIT_PROC:
if (pid > 0)
break;
sub_info->retval = pid;
- /* FALLTHROUGH */
-
- case UMH_WAIT_EXEC:
- complete(sub_info->complete);
+ break;
}
}
_
Patches currently in -mm which might be from nhorman@xxxxxxxxxxxxx are
linux-next.patch
kmod-fix-race-in-usermodehelper-code.patch
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