From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: Re: linux-next: BUG: KASAN: use-after-free in tun_chr_close Date: Wed, 16 May 2018 15:32:59 +0800 Message-ID: <9a7440ca-05dd-7ff6-0fa0-a96afc9ed780@redhat.com> References: <20180516062825.GA11416@outlook.office365.com> <20180516071224.GB11416@outlook.office365.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="------------F3E7A15AA8CBC7CEA6362F07" To: Andrei Vagin , netdev@vger.kernel.org Return-path: Received: from mx3-rdu2.redhat.com ([66.187.233.73]:55496 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751151AbeEPHdE (ORCPT ); Wed, 16 May 2018 03:33:04 -0400 In-Reply-To: <20180516071224.GB11416@outlook.office365.com> Content-Language: en-US Sender: netdev-owner@vger.kernel.org List-ID: This is a multi-part message in MIME format. --------------F3E7A15AA8CBC7CEA6362F07 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 2018年05月16日 15:12, Andrei Vagin wrote: > Hi Jason, > > I think the problem is in "tun: hold a tun socket during ptr_ring_cleanup". > > Pls take a look at the attached patch. Yes. It looks to me it's not necessary to take extra refcnt during release, we can just do the cleanup at __tun_detach(). Could you help to test the attached patch? Thanks --------------F3E7A15AA8CBC7CEA6362F07 Content-Type: text/x-patch; name="0001-tuntap-fix-use-after-free-during-release.patch" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="0001-tuntap-fix-use-after-free-during-release.patch" >>From 4b5ad75208e379dcb32abb9ac4790a0446f8558b Mon Sep 17 00:00:00 2001 From: Jason Wang Date: Wed, 16 May 2018 15:26:52 +0800 Subject: [PATCH] tuntap: fix use after free during release After commit b196d88aba8a ("tun: fix use after free for ptr_ring") we need clean up tx ring during release(). But unfortunately, it tries to do the cleanup after socket were destroyed which will lead another use-after-free. Fix this by doing the cleanup before dropping the last reference of the socket in __tun_detach(). Reported-by: Andrei Vagin Fixes: b196d88aba8a ("tun: fix use after free for ptr_ring") Signed-off-by: Jason Wang --- drivers/net/tun.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/net/tun.c b/drivers/net/tun.c index 9fbbb32..d45ac37 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -729,6 +729,7 @@ static void __tun_detach(struct tun_file *tfile, bool clean) } if (tun) xdp_rxq_info_unreg(&tfile->xdp_rxq); + ptr_ring_cleanup(&tfile->tx_ring, tun_ptr_free); sock_put(&tfile->sk); } } @@ -3245,7 +3246,6 @@ static int tun_chr_close(struct inode *inode, struct file *file) struct tun_file *tfile = file->private_data; tun_detach(tfile, true); - ptr_ring_cleanup(&tfile->tx_ring, tun_ptr_free); return 0; } -- 2.7.4 --------------F3E7A15AA8CBC7CEA6362F07--