net: avoid signed overflows for SO_{SND|RCV}BUFFORCE (CVE-2016-9793)

debian/changelog

@@ -46,6 +46,7 @@ linux (4.8.12-1) UNRELEASED; urgency=medium
   [ Salvatore Bonaccorso ]
   * tipc: check minimum bearer MTU (CVE-2016-8632)
   * packet: fix race condition in packet_set_ring (CVE-2016-8655)
+  * net: avoid signed overflows for SO_{SND|RCV}BUFFORCE (CVE-2016-9793)
 
  -- Uwe Kleine-König <ukleinek@debian.org>  Sun, 04 Dec 2016 21:16:06 +0100
 

debian/patches/bugfix/all/net-avoid-signed-overflows-for-SO_-SND-RCV-BUFFORCE.patch

@@ -0,0 +1,49 @@
+From: Eric Dumazet <edumazet@google.com>
+Date: Fri, 2 Dec 2016 09:44:53 -0800
+Subject: net: avoid signed overflows for SO_{SND|RCV}BUFFORCE
+Origin: https://git.kernel.org/linus/b98b0bc8c431e3ceb4b26b0dfc8db509518fb290
+
+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>
+---
+ 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 5e3ca41..00a074d 100644
+--- a/net/core/sock.c
++++ b/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);
+ 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 @@ 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);
+ 		break;
+ 
+ 	case SO_RCVBUFFORCE:
+-- 
+2.1.4
+

debian/patches/series

@@ -104,6 +104,7 @@ bugfix/all/vfio-pci-Fix-integer-overflows-bitmask-check.patch
 bugfix/all/mnt-Add-a-per-mount-namespace-limit-on-the-number-of.patch
 bugfix/all/tipc-check-minimum-bearer-MTU.patch
 bugfix/all/packet-fix-race-condition-in-packet_set_ring.patch
+bugfix/all/net-avoid-signed-overflows-for-SO_-SND-RCV-BUFFORCE.patch
 
 # ABI maintenance