From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758188Ab3DDKhO (ORCPT ); Thu, 4 Apr 2013 06:37:14 -0400 Received: from out02.mta.xmission.com ([166.70.13.232]:35282 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752692Ab3DDKhM (ORCPT ); Thu, 4 Apr 2013 06:37:12 -0400 From: ebiederm@xmission.com (Eric W. Biederman) To: dingtianhong Cc: "David S. Miller" , Sven Joachim , Greg Kroah-Hartman , , , Eric Dumazet , Andy Lutomirski , Karel Srot , , Eric Dumazet References: <20130402221104.163133110@linuxfoundation.org> <20130402221116.307254752@linuxfoundation.org> <87vc833kpf.fsf@turtle.gmx.de> <87k3ojnosa.fsf@xmission.com> <1365034777.13853.46.camel@edumazet-glaptop> <1365035424.13853.48.camel@edumazet-glaptop> <878v4zjei0.fsf@xmission.com> <87li8zhwkw.fsf_-_@xmission.com> <87d2ubhwiw.fsf_-_@xmission.com> <515D3235.7080608@huawei.com> Date: Thu, 04 Apr 2013 03:36:56 -0700 In-Reply-To: <515D3235.7080608@huawei.com> (dingtianhong@huawei.com's message of "Thu, 4 Apr 2013 15:56:37 +0800") Message-ID: <874nfmeg53.fsf@xmission.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-AID: U2FsdGVkX18Aeug/ZBkIHbHhNGnzLww3hUJl/QUXkOM= X-SA-Exim-Connect-IP: 98.207.154.105 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-Report: * -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP * 1.7 KHOP_BIG_TO_CC Sent to 10+ recipients instaed of Bcc or a list * 1.5 XMNoVowels Alpha-numberic number with no vowels * 0.1 XMSubLong Long Subject * 0.0 T_TM2_M_HEADER_IN_MSG BODY: T_TM2_M_HEADER_IN_MSG * -3.0 BAYES_00 BODY: Bayes spam probability is 0 to 1% * [score: 0.0000] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa01 1397; Body=1 Fuz1=1 Fuz2=1] * 0.0 T_TooManySym_01 4+ unique symbols in subject * 0.0 T_XMDrugObfuBody_08 obfuscated drug references * 0.0 T_TooManySym_02 5+ unique symbols in subject X-Spam-DCC: XMission; sa01 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;dingtianhong X-Spam-Relay-Country: Subject: Re: [PATCH 2/2] af_unix: If we don't care about credentials coallesce all messages X-Spam-Flag: No X-SA-Exim-Version: 4.2.1 (built Wed, 14 Nov 2012 14:26:46 -0700) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org dingtianhong writes: > On 2013/4/4 10:14, Eric W. Biederman wrote: >> >> 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 >> Reported-by: Ding Tianhong >> Signed-off-by: "Eric W. Biederman" >> --- >> 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; >> > > As your opinion, I think the way is better: > > if (test_bit(SOCK_PASSCRED, &sock->flags)) { > if (check_creds) { > /* Never glue messages from different writers */ > if ((UNIXCB(skb).pid != siocb->scm->pid) || > (UNIXCB(skb).cred != siocb->scm->cred)) > break; > } else { > /* Copy credentials */ > scm_set_cred(siocb->scm, UNIXCB(skb).pid, UNIXCB(skb).cred); > check_creds = 1; > } > } It is a smidge clearer in intent, but there is no functional difference. The lines get really long. Shrug. Patches are always welcome. Beyond getting something correct for the right reasons I don't care. Eric