From 05c824cea44ddb773182ac849276a2e0419e3ab2 Mon Sep 17 00:00:00 2001 From: Xufeng Zhang Date: Tue, 21 Jun 2011 10:43:39 +0000 Subject: [PATCH] ipv6/udp: Use the correct variable to determine non-blocking condition [ 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 Signed-off-by: Paul Gortmaker Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- 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 e55aa9c408da..e363c6c76af9 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; } -- 2.39.5