Commit b98b0bc8 authored Dec 02, 2016 by Eric Dumazet Committed by David S. Miller Dec 02, 2016

net: avoid signed overflows for SO_{SND|RCV}BUFFORCE



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 82981930 ("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>

parent 5b010147

net/core/sock.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -715,7 +715,7 @@ 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;
		@@ -751,7 +751,7 @@ 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:

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