| From bd1789ad1bec25dd89a1d13781c0a6e5e40288f3 Mon Sep 17 00:00:00 2001 |
| From: Xufeng Zhang <xufeng.zhang@windriver.com> |
| Date: Tue, 21 Jun 2011 10:43:39 +0000 |
| Subject: [PATCH] ipv6/udp: Use the correct variable to determine non-blocking |
| condition |
| |
| 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 |
| |