linux-kernel - [PATCH 1/1] usermodehelper: check subprocess

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Message-ID: <20130516154355.GB19060@redhat.com>
Date:	Thu, 16 May 2013 17:43:55 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Colin Walters <walters@...bum.org>,
	Denys Vlasenko <vda.linux@...glemail.com>,
	Jiri Slaby <jslaby@...e.cz>,
	Lennart Poettering <mzxreary@...inter.de>,
	Lucas De Marchi <lucas.de.marchi@...il.com>,
	Neil Horman <nhorman@...driver.com>, security@...nel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 1/1] usermodehelper: check subprocess_info->path != NULL

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@...hat.com>
Cc: stable@...r.kernel.org
---
 kernel/kmod.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/kernel/kmod.c b/kernel/kmod.c
index 1296e72..8241906 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -569,6 +569,11 @@ 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;
 
-- 
1.5.5.1


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