From patchwork Wed Jul 6 14:41:13 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: [2/2] tcp: Increase TCP_MAXSEG socket option minimum CVE-2010-4165 Date: Wed, 06 Jul 2011 04:41:13 -0000 From: Paolo Pisati X-Patchwork-Id: 103491 Message-Id: <1309963273-7247-3-git-send-email-paolo.pisati@canonical.com> To: kernel-team@lists.ubuntu.com From: "David S. Miller" BugLink: http://bugs.launchpad.net/bugs/806374 commit upstream 7a1abd08d52fdeddb3e9a5a33f2f15cc6a5674d2 As noted by Steve Chen, since commit f5fff5dc8a7a3f395b0525c02ba92c95d42b7390 ("tcp: advertise MSS requested by user") we can end up with a situation where tcp_select_initial_window() does a divide by a zero (or even negative) mss value. The problem is that sometimes we effectively subtract TCPOLEN_TSTAMP_ALIGNED and/or TCPOLEN_MD5SIG_ALIGNED from the mss. Fix this by increasing the minimum from 8 to 64. CVE-2010-4165 Reported-by: Steve Chen Signed-off-by: David S. Miller Signed-off-by: Paolo Pisati --- net/ipv4/tcp.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 4305154..4174f20 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -1826,7 +1826,7 @@ static int do_tcp_setsockopt(struct sock *sk, int level, /* Values greater than interface MTU won't take effect. However * at the point when this call is done we typically don't yet * know which interface is going to be used */ - if (val < 8 || val > MAX_TCP_WINDOW) { + if (val < 64 || val > MAX_TCP_WINDOW) { err = -EINVAL; break; }