Messages in this thread Patch in this message |  | | | Date | Thu, 07 Jul 2011 17:15:47 -0700 | | From | Greg KH <> | | Subject | [015/107] ipv6/udp: Use the correct variable to determine non-blocking condition |
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2.6.39-stable review patch. If anyone has any objections, please let us know.
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From: Xufeng Zhang <xufeng.zhang@windriver.com>
[ 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 <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: Greg Kroah-Hartman <gregkh@suse.de> --- 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; }
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