[ 3.8.y.z extended stable ] Patch "usermodehelper: check subprocess_info->path != NULL" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    usermodehelper: check subprocess_info->path != NULL

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From e575fb9a2f54ae0384a7cc5c7ecac56ac6ae8b25 Mon Sep 17 00:00:00 2001
From: Oleg Nesterov <oleg at redhat.com>
Date: Thu, 16 May 2013 17:43:55 +0200
Subject: usermodehelper: check subprocess_info->path != NULL

commit 264b83c07a84223f0efd0d1db9ccc66d6f88288f upstream.

argv_split(empty_or_all_spaces) happily succeeds, it simply returns
argc == 0 and argv[0] == NULL. Change call_usermodehelper_exec() to
check sub_info->path != NULL to avoid the crash.

This is the minimal fix, todo:

 - perhaps we should change argv_split() to return NULL or change the
   callers.

 - kill or justify ->path[0] check

 - narrow the scope of helper_lock()

Signed-off-by: Oleg Nesterov <oleg at redhat.com>
Acked-By: Lucas De Marchi <lucas.demarchi at intel.com>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 kernel/kmod.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/kmod.c b/kernel/kmod.c
index 0023a87..41e1524 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -561,6 +561,11 @@ int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
 	int retval = 0;

 	helper_lock();
+	if (!sub_info->path) {
+		retval = -EINVAL;
+		goto out;
+	}
+
 	if (sub_info->path[0] == '\0')
 		goto out;

--
1.8.1.2