linux-kernel - [PATCH 3.18 13/23] net: fix rtnh

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Date:   Mon, 14 May 2018 08:48:42 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
        syzbot <syzkaller@...glegroups.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 3.18 13/23] net: fix rtnh_ok()

3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <edumazet@...gle.com>

commit b1993a2de12c9e75c35729e2ffbc3a92d50c0d31 upstream.

syzbot reported :

BUG: KMSAN: uninit-value in rtnh_ok include/net/nexthop.h:11 [inline]
BUG: KMSAN: uninit-value in fib_count_nexthops net/ipv4/fib_semantics.c:469 [inline]
BUG: KMSAN: uninit-value in fib_create_info+0x554/0x8d20 net/ipv4/fib_semantics.c:1091

@remaining is an integer, coming from user space.
If it is negative we want rtnh_ok() to return false.

Fixes: 4e902c57417c ("[IPv4]: FIB configuration using struct fib_config")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Reported-by: syzbot <syzkaller@...glegroups.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 include/net/nexthop.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/include/net/nexthop.h
+++ b/include/net/nexthop.h
@@ -6,7 +6,7 @@
 
 static inline int rtnh_ok(const struct rtnexthop *rtnh, int remaining)
 {
-	return remaining >= sizeof(*rtnh) &&
+	return remaining >= (int)sizeof(*rtnh) &&
 	       rtnh->rtnh_len >= sizeof(*rtnh) &&
 	       rtnh->rtnh_len <= remaining;
 }