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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 8298193 ("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 <>
Reported-by: Andrey Konovalov <>
Signed-off-by: David S. Miller <>
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Eric Dumazet authored and davem330 committed Dec 2, 2016
1 parent 5b01014 commit b98b0bc8c431e3ceb4b26b0dfc8db509518fb290
Showing with 2 additions and 2 deletions.
  1. +2 −2 net/core/sock.c
@@ -715,7 +715,7 @@ 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. */
@@ -751,7 +751,7 @@ int sock_setsockopt(struct socket *sock, int level, int optname,
* 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);


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