Messages in this thread Patch in this message | | | From | Paul Gortmaker <> | Subject | [34-longterm 103/179] ipv6/udp: Use the correct variable to determine non-blocking condition | Date | Mon, 14 May 2012 22:13:19 -0400 |
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From: Xufeng Zhang <xufeng.zhang@windriver.com>
------------------- This is a commit scheduled for the next v2.6.34 longterm release. http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git If you see a problem with using this for longterm, please comment. -------------------
commit 32c90254ed4a0c698caa0794ebb4de63fcc69631 upstream.
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@windriver.com> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> --- net/ipv6/udp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c index 479f926..a0a6a08 100644 --- a/net/ipv6/udp.c +++ b/net/ipv6/udp.c @@ -441,7 +441,7 @@ csum_copy_err: } release_sock(sk); - if (flags & MSG_DONTWAIT) + if (noblock) return -EAGAIN; goto try_again; } -- 1.7.9.6
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