From: ebiederm@xmission•com (Eric W. Biederman)
To: "David S. Miller" <davem@davemloft•net>
Cc: Sven Joachim <svenjoac@gmx•de>,
Greg Kroah-Hartman <gregkh@linuxfoundation•org>,
linux-kernel@vger•kernel.org, stable@vger•kernel.org,
Ding Tianhong <dingtianhong@huawei•com>,
Eric Dumazet <edumazet@google•com>,
Andy Lutomirski <luto@amacapital•net>,
Karel Srot <ksrot@redhat•com>, <netdev@vger•kernel.org>,
Eric Dumazet <eric.dumazet@gmail•com>
Subject: [PATCH 2/2] af_unix: If we don't care about credentials coallesce all messages
Date: Wed, 03 Apr 2013 19:14:47 -0700 [thread overview]
Message-ID: <87d2ubhwiw.fsf_-_@xmission.com> (raw)
In-Reply-To: <87li8zhwkw.fsf_-_@xmission.com> (Eric W. Biederman's message of "Wed, 03 Apr 2013 19:13:35 -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@redhat•com>
Reported-by: Ding Tianhong <dingtianhong@huawei•com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission•com>
---
net/unix/af_unix.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index f153a8d..2db702d 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1993,7 +1993,7 @@ again:
if ((UNIXCB(skb).pid != siocb->scm->pid) ||
(UNIXCB(skb).cred != siocb->scm->cred))
break;
- } else {
+ } else if (test_bit(SOCK_PASSCRED, &sock->flags)) {
/* Copy credentials */
scm_set_cred(siocb->scm, UNIXCB(skb).pid, UNIXCB(skb).cred);
check_creds = 1;
--
1.7.5.4
next prev parent reply other threads:[~2013-04-04 2:14 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20130402221104.163133110@linuxfoundation.org>
[not found] ` <20130402221116.307254752@linuxfoundation.org>
[not found] ` <87vc833kpf.fsf@turtle.gmx.de>
[not found] ` <87k3ojnosa.fsf@xmission.com>
[not found] ` <1365034777.13853.46.camel@edumazet-glaptop>
[not found] ` <1365035424.13853.48.camel@edumazet-glaptop>
[not found] ` <878v4zjei0.fsf@xmission.com>
2013-04-04 2:13 ` [PATCH 1/2] Revert "af_unix: dont send SCM_CREDENTIAL when dest socket is NULL" Eric W. Biederman
2013-04-04 2:14 ` Eric W. Biederman [this message]
2013-04-04 3:28 ` [PATCH 3/2] scm: Stop passing struct cred Eric W. Biederman
2013-04-05 4:47 ` David Miller
2013-04-04 7:56 ` [PATCH 2/2] af_unix: If we don't care about credentials coallesce all messages dingtianhong
2013-04-04 10:36 ` Eric W. Biederman
2013-04-05 4:47 ` David Miller
2013-04-04 7:51 ` [PATCH 1/2] Revert "af_unix: dont send SCM_CREDENTIAL when dest socket is NULL" dingtianhong
2013-04-04 10:22 ` Eric W. Biederman
2013-04-05 4:47 ` David Miller
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