linux-kernel - [PATCH] sysctl: don't read uninit memory in deprecated_sysctl

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Message-Id: <20170628150037.3809-1-glider@google.com>
Date:   Wed, 28 Jun 2017 17:00:37 +0200
From:   Alexander Potapenko <glider@...gle.com>
To:     dvyukov@...gle.com, kcc@...gle.com, davem@...emloft.net,
        akpm@...ux-foundation.org
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH] sysctl: don't read uninit memory in deprecated_sysctl_warning()

Don't attempt to read the first two elements of name[] unless they
were actually copied from the userspace.

This bug has been detected by KMSAN.

Signed-off-by: Alexander Potapenko <glider@...gle.com>
---
 kernel/sysctl_binary.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sysctl_binary.c b/kernel/sysctl_binary.c
index ece4b177052b..38d6ba22a209 100644
--- a/kernel/sysctl_binary.c
+++ b/kernel/sysctl_binary.c
@@ -1346,7 +1346,7 @@ static void deprecated_sysctl_warning(const int *name, int nlen)
 	 * CTL_KERN/KERN_VERSION is used by older glibc and cannot
 	 * ever go away.
 	 */
-	if (name[0] == CTL_KERN && name[1] == KERN_VERSION)
+	if (nlen >= 2 && name[0] == CTL_KERN && name[1] == KERN_VERSION)
 		return;
 
 	if (printk_ratelimit()) {
-- 
2.13.2.725.g09c95d1e9-goog