This is a note to let you know that I've just added the patch titled
ipv6/udp: Use the correct variable to determine non-blocking condition
to the 2.6.39-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
ipv6-udp-use-the-correct-variable-to-determine-non-blocking-condition.patch
and it can be found in the queue-2.6.39 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 426f44b84f96244914a642bb63d40e1e0f064672 Mon Sep 17 00:00:00 2001
From: Xufeng Zhang <[email protected]>
Date: Tue, 21 Jun 2011 10:43:39 +0000
Subject: ipv6/udp: Use the correct variable to determine non-blocking condition
From: Xufeng Zhang <[email protected]>
[ Upstream commit 32c90254ed4a0c698caa0794ebb4de63fcc69631 ]
udpv6_recvmsg() function is not using the correct variable to determine
whether or not the socket is in non-blocking operation, this will lead
to unexpected behavior when a UDP checksum error occurs.
Consider a non-blocking udp receive scenario: when udpv6_recvmsg() is
called by sock_common_recvmsg(), MSG_DONTWAIT bit of flags variable in
udpv6_recvmsg() is cleared by "flags & ~MSG_DONTWAIT" in this call:
err = sk->sk_prot->recvmsg(iocb, sk, msg, size, flags & MSG_DONTWAIT,
flags & ~MSG_DONTWAIT, &addr_len);
i.e. with udpv6_recvmsg() getting these values:
int noblock = flags & MSG_DONTWAIT
int flags = flags & ~MSG_DONTWAIT
So, when udp checksum error occurs, the execution will go to
csum_copy_err, and then the problem happens:
csum_copy_err:
...............
if (flags & MSG_DONTWAIT)
return -EAGAIN;
goto try_again;
...............
But it will always go to try_again as MSG_DONTWAIT has been cleared
from flags at call time -- only noblock contains the original value
of MSG_DONTWAIT, so the test should be:
if (noblock)
return -EAGAIN;
This is also consistent with what the ipv4/udp code does.
Signed-off-by: Xufeng Zhang <[email protected]>
Signed-off-by: Paul Gortmaker <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
net/ipv6/udp.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -453,7 +453,7 @@ csum_copy_err:
}
unlock_sock_fast(sk, slow);
- if (flags & MSG_DONTWAIT)
+ if (noblock)
return -EAGAIN;
goto try_again;
}
Patches currently in stable-queue which might be from
[email protected] are
queue-2.6.39/udp-recvmsg-clear-msg_trunc-flag-when-starting-over-for-a-new-packet.patch
queue-2.6.39/ipv6-udp-use-the-correct-variable-to-determine-non-blocking-condition.patch
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