netdev - [PATCH v1 1/1] mac_pton: Don't access memory over expected length

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Message-Id: <20221005164301.14381-1-andriy.shevchenko@linux.intel.com>
Date:   Wed,  5 Oct 2022 19:43:01 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH v1 1/1] mac_pton: Don't access memory over expected length

The strlen() may go too far when estimating the length of
the given string. In some cases it may go over the boundary
and crash the system which is the case according to the commit
13a55372b64e ("ARM: orion5x: Revert commit 4904dbda41c8.").

Rectify this by switching to strnlen() for the expected
maximum length of the string.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
---
 lib/net_utils.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/net_utils.c b/lib/net_utils.c
index af525353395d..c17201df3d08 100644
--- a/lib/net_utils.c
+++ b/lib/net_utils.c
@@ -6,10 +6,11 @@
 
 bool mac_pton(const char *s, u8 *mac)
 {
+	size_t maxlen = 3 * ETH_ALEN - 1;
 	int i;
 
 	/* XX:XX:XX:XX:XX:XX */
-	if (strlen(s) < 3 * ETH_ALEN - 1)
+	if (strnlen(s, maxlen) < maxlen)
 		return false;
 
 	/* Don't dirty result unless string is valid MAC. */
-- 
2.35.1