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Date: Wed, 10 Nov 2010 21:36:24 -0800 (PST)
From: David Miller <davem@...emloft.net>
To: shanwei@...fujitsu.com
Cc: schen@...sta.com, netdev@...r.kernel.org
Subject: Re: possible kernel oops from user MSS
From: David Miller <davem@...emloft.net>
Date: Wed, 10 Nov 2010 21:33:13 -0800 (PST)
> I'll make the minimum 64 or something like that.
Here is the patch I will use:
--------------------
tcp: Increase TCP_MAXSEG socket option minimum.
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.
Reported-by: Steve Chen <schen@...sta.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
---
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 245603c..0814199 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2246,7 +2246,7 @@ 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;
}
--
1.7.3.2
--
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