From: ebiederm@xxxxxxxxxxxx (Eric W. Biederman) Date: Wed, 03 Apr 2013 19:14:47 -0700 > > It was reported that the following LSB test case failed > https://lsbbugs.linuxfoundation.org/attachment.cgi?id=2144 because we > were not coallescing unix stream messages when the application was > expecting us to. > > The problem was that the first send was before the socket was accepted > and thus sock->sk_socket was NULL in maybe_add_creds, and the second > send after the socket was accepted had a non-NULL value for sk->socket > and thus we could tell the credentials were not needed so we did not > bother. > > The unnecessary credentials on the first message cause > unix_stream_recvmsg to start verifying that all messages had the same > credentials before coallescing and then the coallescing failed because > the second message had no credentials. > > Ignoring credentials when we don't care in unix_stream_recvmsg fixes a > long standing pessimization which would fail to coallesce messages when > reading from a unix stream socket if the senders were different even if > we did not care about their credentials. > > I have tested this and verified that the in the LSB test case mentioned > above that the messages do coallesce now, while the were failing to > coallesce without this change. > > Reported-by: Karel Srot <ksrot@xxxxxxxxxx> > Reported-by: Ding Tianhong <dingtianhong@xxxxxxxxxx> > Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx> Applied. -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html