Re: possible kernel oops from user MSS

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

From: David Miller <davem@xxxxxxxxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
---
 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

--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html


[Linux Kernel Discussion]     [Ethernet Bridging]     [Linux Wireless Networking]     [Linux Bluetooth Networking]     [Linux Networking Users]     [VLAN]     [Git]     [IETF Annouce]     [Linux Assembly]     [Security]     [Bugtraq]     [Photo]     [Singles Social Networking]     [Yosemite Information]     [MIPS Linux]     [ARM Linux Kernel]     [ARM Linux]     [Linux Virtualization]     [Linux Security]     [Linux IDE]     [Linux RAID]     [Linux SCSI]     [Free Dating]

Add to Google Powered by Linux