net: avoid signed overflows for SO_{SND|RCV}BUFFORCE
Eric Dumazet [Fri, 2 Dec 2016 17:44:53 +0000 (09:44 -0800)]
CAP_NET_ADMIN users should not be allowed to set negative
sk_sndbuf or sk_rcvbuf values, as it can lead to various memory
corruptions, crashes, OOM...

Note that before commit 82981930125a ("net: cleanups in
sock_setsockopt()"), the bug was even more serious, since SO_SNDBUF
and SO_RCVBUF were vulnerable.

This needs to be backported to all known linux kernels.

Again, many thanks to syzkaller team for discovering this gem.

Bug 1880704

Change-Id: I26b2411b5a5fd532fa8c02e2c68d0ec9acb784b1
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Gagan Grover <ggrover@nvidia.com>
Reviewed-on: http://git-master/r/1311861
(cherry picked from commit f459cad9a16059c8dbebb9a092ae172ea4a86235)
Reviewed-on: http://git-master/r/1314069
(cherry picked from commit 59df690ce8a50ea463e93ecc65dd897833cc54ad)
Reviewed-on: http://git-master/r/1455429
Reviewed-by: Manish Tuteja <mtuteja@nvidia.com>
Tested-by: Manish Tuteja <mtuteja@nvidia.com>

net/core/sock.c

index bc9db12..cac5926 100644 (file)
@@ -727,7 +727,7 @@ int sock_setsockopt(struct socket *sock, int level, int optname,
                val = min_t(u32, val, sysctl_wmem_max);
 set_sndbuf:
                sk->sk_userlocks |= SOCK_SNDBUF_LOCK;
-               sk->sk_sndbuf = max_t(u32, val * 2, SOCK_MIN_SNDBUF);
+               sk->sk_sndbuf = max_t(int, val * 2, SOCK_MIN_SNDBUF);
                /* Wake up sending tasks if we upped the value. */
                sk->sk_write_space(sk);
                break;
@@ -763,7 +763,7 @@ set_rcvbuf:
                 * returning the value we actually used in getsockopt
                 * is the most desirable behavior.
                 */
-               sk->sk_rcvbuf = max_t(u32, val * 2, SOCK_MIN_RCVBUF);
+               sk->sk_rcvbuf = max_t(int, val * 2, SOCK_MIN_RCVBUF);
                break;
 
        case SO_RCVBUFFORCE: