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Message-Id: <1308689020-1873-3-git-send-email-paul.gortmaker@windriver.com>
Date: Tue, 21 Jun 2011 16:43:39 -0400
From: Paul Gortmaker <paul.gortmaker@...driver.com>
To: davem@...emloft.net, eric.dumazet@...il.com
Cc: netdev@...r.kernel.org, Xufeng Zhang <xufeng.zhang@...driver.com>,
Paul Gortmaker <paul.gortmaker@...driver.com>
Subject: [PATCH net-next 2/3] ipv6/udp: Use the correct variable to determine non-blocking condition
From: Xufeng Zhang <xufeng.zhang@...driver.com>
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 <xufeng.zhang@...driver.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@...driver.com>
---
net/ipv6/udp.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 41f8c9c..1e7a43f 100644
--- 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;
}
--
1.7.4.4
--
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