Commit 4c1c7be9 authored Sep 30, 2013 by Tetsuo Handa Committed by Linus Torvalds Sep 30, 2013

kernel/kmod.c: check for NULL in call_usermodehelper_exec()



If /proc/sys/kernel/core_pattern contains only "|", a NULL pointer
dereference happens upon core dump because argv_split("") returns
argv[0] == NULL.

This bug was once fixed by commit 264b83c0 ("usermodehelper: check
subprocess_info->path != NULL") but was by error reintroduced by commit
7f57cfa4 ("usermodehelper: kill the sub_info->path[0] check").

This bug seems to exist since 2.6.19 (the version which core dump to
pipe was added).  Depending on kernel version and config, some side
effect might happen immediately after this oops (e.g.  kernel panic with
2.6.32-358.18.1.el6).

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent d8c63376

kernel/kmod.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -571,6 +571,10 @@ int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
		DECLARE_COMPLETION_ONSTACK(done);
		int retval = 0;

		if (!sub_info->path) {
		call_usermodehelper_freeinfo(sub_info);
		return -EINVAL;
		}
		helper_lock();
		if (!khelper_wq \|\| usermodehelper_disabled) {
		retval = -EBUSY;