From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751413AbdAQVYc (ORCPT ); Tue, 17 Jan 2017 16:24:32 -0500 Received: from mail-wm0-f65.google.com ([74.125.82.65]:34210 "EHLO mail-wm0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750888AbdAQVWy (ORCPT ); Tue, 17 Jan 2017 16:22:54 -0500 MIME-Version: 1.0 In-Reply-To: References: <20161209013208.GW1555@ZenIV.linux.org.uk> <20161209064144.GZ1555@ZenIV.linux.org.uk> From: Cong Wang Date: Tue, 17 Jan 2017 13:21:48 -0800 Message-ID: Subject: Re: fs, net: deadlock between bind/splice on af_unix To: Dmitry Vyukov Cc: Al Viro , "linux-fsdevel@vger.kernel.org" , LKML , David Miller , Rainer Weikusat , Hannes Frederic Sowa , netdev , Eric Dumazet , syzkaller Content-Type: multipart/mixed; boundary=001a114b9db08da50c054650e463 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --001a114b9db08da50c054650e463 Content-Type: text/plain; charset=UTF-8 On Mon, Jan 16, 2017 at 1:32 AM, Dmitry Vyukov wrote: > On Fri, Dec 9, 2016 at 7:41 AM, Al Viro wrote: >> On Thu, Dec 08, 2016 at 10:32:00PM -0800, Cong Wang wrote: >> >>> > Why do we do autobind there, anyway, and why is it conditional on >>> > SOCK_PASSCRED? Note that e.g. for SOCK_STREAM we can bloody well get >>> > to sending stuff without autobind ever done - just use socketpair() >>> > to create that sucker and we won't be going through the connect() >>> > at all. >>> >>> In the case Dmitry reported, unix_dgram_sendmsg() calls unix_autobind(), >>> not SOCK_STREAM. >> >> Yes, I've noticed. What I'm asking is what in there needs autobind triggered >> on sendmsg and why doesn't the same need affect the SOCK_STREAM case? >> >>> I guess some lock, perhaps the u->bindlock could be dropped before >>> acquiring the next one (sb_writer), but I need to double check. >> >> Bad idea, IMO - do you *want* autobind being able to come through while >> bind(2) is busy with mknod? > > > Ping. This is still happening on HEAD. > Thanks for your reminder. Mind to give the attached patch (compile only) a try? I take another approach to fix this deadlock, which moves the unix_mknod() out of unix->bindlock. Not sure if there is any unexpected impact with this way. Thanks. --001a114b9db08da50c054650e463 Content-Type: text/plain; charset=US-ASCII; name="unix.diff" Content-Disposition: attachment; filename="unix.diff" Content-Transfer-Encoding: base64 X-Attachment-Id: f_iy20ypnl0 ZGlmZiAtLWdpdCBhL25ldC91bml4L2FmX3VuaXguYyBiL25ldC91bml4L2FmX3VuaXguYwppbmRl eCAxMjc2NTZlLi41ZDRiNGQxIDEwMDY0NAotLS0gYS9uZXQvdW5peC9hZl91bml4LmMKKysrIGIv bmV0L3VuaXgvYWZfdW5peC5jCkBAIC05OTUsNiArOTk1LDcgQEAgc3RhdGljIGludCB1bml4X2Jp bmQoc3RydWN0IHNvY2tldCAqc29jaywgc3RydWN0IHNvY2thZGRyICp1YWRkciwgaW50IGFkZHJf bGVuKQogCXVuc2lnbmVkIGludCBoYXNoOwogCXN0cnVjdCB1bml4X2FkZHJlc3MgKmFkZHI7CiAJ c3RydWN0IGhsaXN0X2hlYWQgKmxpc3Q7CisJc3RydWN0IHBhdGggcGF0aDsKIAogCWVyciA9IC1F SU5WQUw7CiAJaWYgKHN1bmFkZHItPnN1bl9mYW1pbHkgIT0gQUZfVU5JWCkKQEAgLTEwMTAsOSAr MTAxMSwyMCBAQCBzdGF0aWMgaW50IHVuaXhfYmluZChzdHJ1Y3Qgc29ja2V0ICpzb2NrLCBzdHJ1 Y3Qgc29ja2FkZHIgKnVhZGRyLCBpbnQgYWRkcl9sZW4pCiAJCWdvdG8gb3V0OwogCWFkZHJfbGVu ID0gZXJyOwogCisJaWYgKHN1bl9wYXRoWzBdKSB7CisJCXVtb2RlX3QgbW9kZSA9IFNfSUZTT0NL IHwKKwkJICAgICAgIChTT0NLX0lOT0RFKHNvY2spLT5pX21vZGUgJiB+Y3VycmVudF91bWFzaygp KTsKKwkJZXJyID0gdW5peF9ta25vZChzdW5fcGF0aCwgbW9kZSwgJnBhdGgpOworCQlpZiAoZXJy KSB7CisJCQlpZiAoZXJyID09IC1FRVhJU1QpCisJCQkJZXJyID0gLUVBRERSSU5VU0U7CisJCQln b3RvIG91dDsKKwkJfQorCX0KKwogCWVyciA9IG11dGV4X2xvY2tfaW50ZXJydXB0aWJsZSgmdS0+ YmluZGxvY2spOwogCWlmIChlcnIpCi0JCWdvdG8gb3V0OworCQlnb3RvIG91dF9wdXQ7CiAKIAll cnIgPSAtRUlOVkFMOwogCWlmICh1LT5hZGRyKQpAQCAtMTAyOSwxNiArMTA0MSw2IEBAIHN0YXRp YyBpbnQgdW5peF9iaW5kKHN0cnVjdCBzb2NrZXQgKnNvY2ssIHN0cnVjdCBzb2NrYWRkciAqdWFk ZHIsIGludCBhZGRyX2xlbikKIAlhdG9taWNfc2V0KCZhZGRyLT5yZWZjbnQsIDEpOwogCiAJaWYg KHN1bl9wYXRoWzBdKSB7Ci0JCXN0cnVjdCBwYXRoIHBhdGg7Ci0JCXVtb2RlX3QgbW9kZSA9IFNf SUZTT0NLIHwKLQkJICAgICAgIChTT0NLX0lOT0RFKHNvY2spLT5pX21vZGUgJiB+Y3VycmVudF91 bWFzaygpKTsKLQkJZXJyID0gdW5peF9ta25vZChzdW5fcGF0aCwgbW9kZSwgJnBhdGgpOwotCQlp ZiAoZXJyKSB7Ci0JCQlpZiAoZXJyID09IC1FRVhJU1QpCi0JCQkJZXJyID0gLUVBRERSSU5VU0U7 Ci0JCQl1bml4X3JlbGVhc2VfYWRkcihhZGRyKTsKLQkJCWdvdG8gb3V0X3VwOwotCQl9CiAJCWFk ZHItPmhhc2ggPSBVTklYX0hBU0hfU0laRTsKIAkJaGFzaCA9IGRfYmFja2luZ19pbm9kZShwYXRo LmRlbnRyeSktPmlfaW5vICYgKFVOSVhfSEFTSF9TSVpFIC0gMSk7CiAJCXNwaW5fbG9jaygmdW5p eF90YWJsZV9sb2NrKTsKQEAgLTEwNjUsNiArMTA2Nyw5IEBAIHN0YXRpYyBpbnQgdW5peF9iaW5k KHN0cnVjdCBzb2NrZXQgKnNvY2ssIHN0cnVjdCBzb2NrYWRkciAqdWFkZHIsIGludCBhZGRyX2xl bikKIAlzcGluX3VubG9jaygmdW5peF90YWJsZV9sb2NrKTsKIG91dF91cDoKIAltdXRleF91bmxv Y2soJnUtPmJpbmRsb2NrKTsKK291dF9wdXQ6CisJaWYgKGVycikKKwkJcGF0aF9wdXQoJnBhdGgp Owogb3V0OgogCXJldHVybiBlcnI7CiB9Cg== --001a114b9db08da50c054650e463--