From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH net] vhost: correctly remove wait queue during poll failure Date: Tue, 27 Mar 2018 16:58:59 +0300 Message-ID: <20180327165330-mutt-send-email-mst@kernel.org> References: <1522122442-30317-1-git-send-email-jasowang@redhat.com> <20180327092811.ikvssyxgb74nucb4@dhcp-10-175-199-170.vpn.oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Jason Wang Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org List-Id: virtualization@lists.linuxfoundation.org T24gVHVlLCBNYXIgMjcsIDIwMTggYXQgMDU6NDM6MTRQTSArMDgwMCwgSmFzb24gV2FuZyB3cm90 ZToKPiAKPiAKPiBPbiAyMDE45bm0MDPmnIgyN+aXpSAxNzoyOCwgRGFycmVuIEtlbm55IHdyb3Rl Ogo+ID4gSGkgSmFzb24sCj4gPiAKPiA+IE9uIFR1ZSwgTWFyIDI3LCAyMDE4IGF0IDExOjQ3OjIy QU0gKzA4MDAsIEphc29uIFdhbmcgd3JvdGU6Cj4gPiA+IFdlIHRyaWVkIHRvIHJlbW92ZSB2cSBw b2xsIGZyb20gd2FpdCBxdWV1ZSwgYnV0IGRvIG5vdCBjaGVjayB3aGV0aGVyCj4gPiA+IG9yIG5v dCBpdCB3YXMgaW4gYSBsaXN0IGJlZm9yZS4gVGhpcyB3aWxsIGxlYWQgZG91YmxlIGZyZWUuIEZp eGluZwo+ID4gPiB0aGlzIGJ5IGNoZWNraW5nIHBvbGwtPndxaCB0byBtYWtlIHN1cmUgaXQgd2Fz IGluIGEgbGlzdC4KPiA+IAo+ID4gVGhpcyB0ZXh0IHNlZW1zIGF0IG9kZHMgd2l0aCB0aGUgY29k ZSBiZWxvdywgaW5zdGVhZCBvZiBjaGVja2luZwo+ID4gcG9sbC13aHEsIHlvdSBhcmUgcmVtb3Zp bmcgdGhhdCBjaGVjay4uLgo+ID4gCj4gPiBNYXliZSB0aGUgdGV4dCBuZWVkcyByZXdvcmRpbmc/ Cj4gCj4gWWVzLCBJIGFkbWl0IGl0J3MgYmFkLCB0aGFua3MgZm9yIHBvaW50aW5nIG91dC4KPiAK PiBIb3cgYWJvdXQ6Cj4gCj4gIkZpeGluZyB0aGlzIGJ5IHN3aXRjaGluZyB0byB1c2Ugdmhvc3Rf cG9sbF9zdG9wKCkgd2hpY2ggemVyb3MgcG9sbC0+d3FoCj4gYWZ0ZXIgcmVtb3ZpbmcgcG9sbCBm cm9tIHdhaXRxdWV1ZSB0byBtYWtlIHN1cmUgaXQgd29uJ3QgYmUgZnJlZWQgdHdpY2UuIgo+IAo+ IFRoYW5rcwoKTGV0J3MgYmUgYSBiaXQgbW9yZSBzcGVjaWZpYyBhYm91dCB0aGUgcHJvYmxlbSBt YXliZT8KCndoZW4gdmhvc3QncyBhdHRlbXB0IHRvIHN0YXJ0IHBvbGxpbmcgYSBkZXNjcmlwdG9y IGZhaWxzLCB3ZSByZW1vdmUgdGhlCnBvbGwtPndxaCBlbnRyeSBmcm9tIHdhaXQgcXVldWUgYnV0 IGRvIG5vdCBjbGVhciBpdCwgc28gdGhlIGZvbGxvd2luZwpjbGVhbnVwIChlLmcuIG9uIHJlbGVh c2UpIHdpbGwgYXR0ZW1wdCB0byByZW1vdmUgaXQgYWdhaW4uCgpUbyBmaXgsIHN3aXRjaCB0byB2 aG9zdF9wb2xsX3N0b3AoKSB3aGljaCB6ZXJvcyBwb2xsLT53cWgKYWZ0ZXIgcmVtb3ZpbmcgcG9s bCBmcm9tIHdhaXRxdWV1ZSB0byBtYWtlIHN1cmUgaXQgd29uJ3QgYmUgZnJlZWQgdHdpY2UuIgoK CnRoZSBwYXRjaCBpdHNlbGYgaXMgZmluZSB0aG91Z2g6CgoKQWNrZWQtYnk6IE1pY2hhZWwgUy4g VHNpcmtpbiA8bXN0QHJlZGhhdC5jb20+CgoKPiA+IAo+ID4gVGhhbmtzLAo+ID4gCj4gPiBEYXJy ZW4uCj4gPiAKPiA+ID4gCj4gPiA+IFJlcG9ydGVkLWJ5OiBzeXpib3QrYzAyNzI5NzJiMDFiODcy ZTYwNGFAc3l6a2FsbGVyLmFwcHNwb3RtYWlsLmNvbQo+ID4gPiBGaXhlczogMmI4YjMyOGI2MWM3 OSAoInZob3N0X25ldDogaGFuZGxlIHBvbGxpbmcgZXJyb3JzIHdoZW4gc2V0dGluZwo+ID4gPiBi YWNrZW5kIikKPiA+ID4gU2lnbmVkLW9mZi1ieTogSmFzb24gV2FuZyA8amFzb3dhbmdAcmVkaGF0 LmNvbT4KPiA+ID4gLS0tCj4gPiA+IGRyaXZlcnMvdmhvc3Qvdmhvc3QuYyB8IDMgKy0tCj4gPiA+ IDEgZmlsZSBjaGFuZ2VkLCAxIGluc2VydGlvbigrKSwgMiBkZWxldGlvbnMoLSkKPiA+ID4gCj4g PiA+IGRpZmYgLS1naXQgYS9kcml2ZXJzL3Zob3N0L3Zob3N0LmMgYi9kcml2ZXJzL3Zob3N0L3Zo b3N0LmMKPiA+ID4gaW5kZXggMWIzZThkMmQuLjVkNWE5ZDkgMTAwNjQ0Cj4gPiA+IC0tLSBhL2Ry aXZlcnMvdmhvc3Qvdmhvc3QuYwo+ID4gPiArKysgYi9kcml2ZXJzL3Zob3N0L3Zob3N0LmMKPiA+ ID4gQEAgLTIxMiw4ICsyMTIsNyBAQCBpbnQgdmhvc3RfcG9sbF9zdGFydChzdHJ1Y3Qgdmhvc3Rf cG9sbCAqcG9sbCwKPiA+ID4gc3RydWN0IGZpbGUgKmZpbGUpCj4gPiA+IMKgwqDCoMKgaWYgKG1h c2spCj4gPiA+IMKgwqDCoMKgwqDCoMKgIHZob3N0X3BvbGxfd2FrZXVwKCZwb2xsLT53YWl0LCAw LCAwLCBwb2xsX3RvX2tleShtYXNrKSk7Cj4gPiA+IMKgwqDCoMKgaWYgKG1hc2sgJiBFUE9MTEVS Uikgewo+ID4gPiAtwqDCoMKgwqDCoMKgwqAgaWYgKHBvbGwtPndxaCkKPiA+ID4gLcKgwqDCoMKg wqDCoMKgwqDCoMKgwqAgcmVtb3ZlX3dhaXRfcXVldWUocG9sbC0+d3FoLCAmcG9sbC0+d2FpdCk7 Cj4gPiA+ICvCoMKgwqDCoMKgwqDCoCB2aG9zdF9wb2xsX3N0b3AocG9sbCk7Cj4gPiA+IMKgwqDC oMKgwqDCoMKgIHJldCA9IC1FSU5WQUw7Cj4gPiA+IMKgwqDCoMKgfQo+ID4gPiAKPiA+ID4gLS0g Cj4gPiA+IDIuNy40Cj4gPiA+IApfX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19f X19fX19fX19fXwpWaXJ0dWFsaXphdGlvbiBtYWlsaW5nIGxpc3QKVmlydHVhbGl6YXRpb25AbGlz dHMubGludXgtZm91bmRhdGlvbi5vcmcKaHR0cHM6Ly9saXN0cy5saW51eGZvdW5kYXRpb24ub3Jn L21haWxtYW4vbGlzdGluZm8vdmlydHVhbGl6YXRpb24= From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753004AbeC0N7C (ORCPT ); Tue, 27 Mar 2018 09:59:02 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:52298 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752590AbeC0N7A (ORCPT ); Tue, 27 Mar 2018 09:59:00 -0400 Date: Tue, 27 Mar 2018 16:58:59 +0300 From: "Michael S. Tsirkin" To: Jason Wang Cc: kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net] vhost: correctly remove wait queue during poll failure Message-ID: <20180327165330-mutt-send-email-mst@kernel.org> References: <1522122442-30317-1-git-send-email-jasowang@redhat.com> <20180327092811.ikvssyxgb74nucb4@dhcp-10-175-199-170.vpn.oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Mar 27, 2018 at 05:43:14PM +0800, Jason Wang wrote: > > > On 2018年03月27日 17:28, Darren Kenny wrote: > > Hi Jason, > > > > On Tue, Mar 27, 2018 at 11:47:22AM +0800, Jason Wang wrote: > > > We tried to remove vq poll from wait queue, but do not check whether > > > or not it was in a list before. This will lead double free. Fixing > > > this by checking poll->wqh to make sure it was in a list. > > > > This text seems at odds with the code below, instead of checking > > poll-whq, you are removing that check... > > > > Maybe the text needs rewording? > > Yes, I admit it's bad, thanks for pointing out. > > How about: > > "Fixing this by switching to use vhost_poll_stop() which zeros poll->wqh > after removing poll from waitqueue to make sure it won't be freed twice." > > Thanks Let's be a bit more specific about the problem maybe? when vhost's attempt to start polling a descriptor fails, we remove the poll->wqh entry from wait queue but do not clear it, so the following cleanup (e.g. on release) will attempt to remove it again. To fix, switch to vhost_poll_stop() which zeros poll->wqh after removing poll from waitqueue to make sure it won't be freed twice." the patch itself is fine though: Acked-by: Michael S. Tsirkin > > > > Thanks, > > > > Darren. > > > > > > > > Reported-by: syzbot+c0272972b01b872e604a@syzkaller.appspotmail.com > > > Fixes: 2b8b328b61c79 ("vhost_net: handle polling errors when setting > > > backend") > > > Signed-off-by: Jason Wang > > > --- > > > drivers/vhost/vhost.c | 3 +-- > > > 1 file changed, 1 insertion(+), 2 deletions(-) > > > > > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > > > index 1b3e8d2d..5d5a9d9 100644 > > > --- a/drivers/vhost/vhost.c > > > +++ b/drivers/vhost/vhost.c > > > @@ -212,8 +212,7 @@ int vhost_poll_start(struct vhost_poll *poll, > > > struct file *file) > > >     if (mask) > > >         vhost_poll_wakeup(&poll->wait, 0, 0, poll_to_key(mask)); > > >     if (mask & EPOLLERR) { > > > -        if (poll->wqh) > > > -            remove_wait_queue(poll->wqh, &poll->wait); > > > +        vhost_poll_stop(poll); > > >         ret = -EINVAL; > > >     } > > > > > > -- > > > 2.7.4 > > >