[for-3.18,6/7] net: avoid signed overflows for SO_{SND|RCV}BUFFORCE

Message ID 1493832958-12489-7-git-send-email-amit.pundir@linaro.org
State New
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Commit Message

Amit Pundir May 3, 2017, 5:35 p.m.
From: Eric Dumazet <edumazet@google.com>

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.

Signed-off-by: Eric Dumazet <edumazet@google.com>

Reported-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

(cherry picked from commit b98b0bc8c431e3ceb4b26b0dfc8db509518fb290)
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>

 net/core/sock.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)



diff --git a/net/core/sock.c b/net/core/sock.c
index 3b3734f81e64..7bcd07e7eeed 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -733,7 +733,7 @@  int sock_setsockopt(struct socket *sock, int level, int optname,
 		val = min_t(u32, val, sysctl_wmem_max);
 		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. */
@@ -769,7 +769,7 @@  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);