From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Woodhouse Subject: Re: Problem with patch "make nlmsg_end() and genlmsg_end() void" Date: Wed, 08 Apr 2015 13:03:22 +0100 Message-ID: <1428494602.9010.11.camel@infradead.org> References: <01A82AB9-6ABD-4AD0-9CBC-628091569DB0@holtmann.org> <20150118.233722.226468667930444145.davem@davemloft.net> Mime-Version: 1.0 Content-Type: multipart/signed; micalg="sha-1"; protocol="application/x-pkcs7-signature"; boundary="=-SIcyPAEcezkA6FJRMkzg" Cc: marcel@holtmann.org, sfeldma@gmail.com, netdev@vger.kernel.org, johannes@sipsolutions.net, teg@jklm.no To: David Miller , torvalds@linux-foundation.org Return-path: Received: from casper.infradead.org ([85.118.1.10]:46640 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751265AbbDHMD1 (ORCPT ); Wed, 8 Apr 2015 08:03:27 -0400 In-Reply-To: <20150118.233722.226468667930444145.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: --=-SIcyPAEcezkA6FJRMkzg Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Sun, 2015-01-18 at 23:37 -0500, David Miller wrote: > From: Marcel Holtmann > Date: Sun, 18 Jan 2015 18:10:46 -0800 >=20 > > Hi Scott, > >=20 > >> This patch needs to be reverted ASAP. git bisect landed me here also; > >> my processes are getting the OOM msgs. What testing was done? > >>=20 > >> Seems someone does care that nlmsg_end() returns skb->len. > >=20 > > I still wonder how this affects userspace. I have not figured that > > out. Something goes wrong pretty badly somewhere. > >=20 > > Have you tried the small diff with the two locations that were > > problematic for me? >=20 > There were a lot more cases not converted properly, I hope the > patch below gets them all. >=20 > Johannes, this was either not tested or tested very poorly, please > don't submit changes like this. Even neighbour entry and route > dumping were hosed. >=20 > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > [PATCH] netlink: Fix bugs in nlmsg_end() conversions. >=20 > Commit 053c095a82cf ("netlink: make nlmsg_end() and genlmsg_end() > void") didn't catch all of the cases where callers were breaking out > on the return value being equal to zero, which they no longer should > when zero means success. >=20 > Fix all such cases. I'm not sure if this is entirely fixed. In Fedora 22 (4.0.0-rc5-git4) I'm occasionally seeing glibc deadlock in __check_pf() on a netlink recvmsg(), here: https://sourceware.org/git/?p=3Dglibc.git;a=3Dblob;f=3Dsysdeps/unix/sysv/li= nux/check_pf.c;h=3D162606d7;hb=3Dglibc-2.21#l166 As I understand it, this shouldn't happen. Even if messages are dropped (which surely shouldn't happen as often as I'm seeing this), glibc should get ENOBUFS from the recvmsg() call. https://bugzilla.redhat.com/show_bug.cgi?id=3D1209433 I haven't bisected and proved that it *was* this commit which introduced the problem, as it only happens after a day or two of running Evolution and I haven't managed to trigger it more reliably. --=20 David Woodhouse Open Source Technology Centre David.Woodhouse@intel.com Intel Corporation --=-SIcyPAEcezkA6FJRMkzg Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExCzAJBgUrDgMCGgUAMIAGCSqGSIb3DQEHAQAAoIISxDCCBjQw ggQcoAMCAQICAR4wDQYJKoZIhvcNAQEFBQAwfTELMAkGA1UEBhMCSUwxFjAUBgNVBAoTDVN0YXJ0 Q29tIEx0ZC4xKzApBgNVBAsTIlNlY3VyZSBEaWdpdGFsIENlcnRpZmljYXRlIFNpZ25pbmcxKTAn BgNVBAMTIFN0YXJ0Q29tIENlcnRpZmljYXRpb24gQXV0aG9yaXR5MB4XDTA3MTAyNDIxMDE1NVoX 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