Commit 32c90254 authored by Xufeng Zhang's avatar Xufeng Zhang Committed by David S. Miller
Browse files

ipv6/udp: Use the correct variable to determine non-blocking condition

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:

            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: default avatarXufeng Zhang <>
Signed-off-by: default avatarPaul Gortmaker <>
Signed-off-by: default avatarDavid S. Miller <>
parent 58fa4597
......@@ -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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