From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id E9255C433F5 for ; Thu, 10 Feb 2022 15:27:56 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 548DC6B0073; Thu, 10 Feb 2022 10:27:56 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 4F6E66B0075; Thu, 10 Feb 2022 10:27:56 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3BE286B007B; Thu, 10 Feb 2022 10:27:56 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0059.hostedemail.com [216.40.44.59]) by kanga.kvack.org (Postfix) with ESMTP id 2E0CF6B0073 for ; Thu, 10 Feb 2022 10:27:56 -0500 (EST) Received: from smtpin15.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id DF773180ACF6C for ; Thu, 10 Feb 2022 15:27:55 +0000 (UTC) X-FDA: 79127250510.15.56F9ABF Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf25.hostedemail.com (Postfix) with ESMTP id 3C15CA0009 for ; Thu, 10 Feb 2022 15:27:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=Gynz4GctFraPlMytzPSTNoFqFWVAHNCc0fOzdQVAQao=; b=NR/BHKdbpQZLlGtoCSDgUNPG7O Psw60z4N0oxcyitqN37cRew0XqRp4cDUPsyKjL0PxURP+FV2ib53eVf1fPPOGC/N0zcMhJgU+3LOB lljmJblJ+yQIlB7KrTDIX9umG6orwo+cfbeelE/IzN3PT3BoEdG7elhwCk399RxvYdd3qcPMYPchy Id+Q1MLy8dTsv2lAzpXdjHR2T90uqUiIF87u2sjzXLMaxoso1KjuH9hb5IIAD24aJTfX8DXZHNj5t 3r+4CIcDjTVb1BtGw2/hXD3f5zknfgMEp2hOx1XOfjHAno8gOPDbmWa/K9JWfXzctbL+QC0eNU+YG frimlstw==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1nIBLm-009XVY-RL; Thu, 10 Feb 2022 15:27:14 +0000 Date: Thu, 10 Feb 2022 15:27:14 +0000 From: Matthew Wilcox To: Suren Baghdasaryan Cc: Michal Hocko , Andrew Morton , Colin Cross , Sumit Semwal , Dave Hansen , Kees Cook , "Kirill A . Shutemov" , Vlastimil Babka , Johannes Weiner , "Eric W. Biederman" , brauner@kernel.org, legion@kernel.org, ran.xiaokai@zte.com.cn, sashal@kernel.org, Chris Hyser , Davidlohr Bueso , Peter Collingbourne , caoxiaofeng@yulong.com, David Hildenbrand , Cyrill Gorcunov , linux-mm , LKML , kernel-team , syzbot+aa7b3d4b35f9dc46a366@syzkaller.appspotmail.com Subject: Re: [PATCH v2 1/1] mm: fix use-after-free when anon vma name is used after vma is freed Message-ID: References: <20220210043215.42794-1-surenb@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Authentication-Results: imf25.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b="NR/BHKdb"; spf=none (imf25.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=none X-Stat-Signature: zpnxash1sm41fw8deau5517eqgjiqzza X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 3C15CA0009 X-Rspam-User: X-HE-Tag: 1644506875-833142 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Feb 10, 2022 at 07:18:24AM -0800, Suren Baghdasaryan wrote: > On Thu, Feb 10, 2022 at 4:40 AM 'Michal Hocko' via kernel-team > wrote: > > > > On Wed 09-02-22 20:32:15, Suren Baghdasaryan wrote: > > > When adjacent vmas are being merged it can result in the vma that was > > > originally passed to madvise_update_vma being destroyed. In the current > > > implementation, the name parameter passed to madvise_update_vma points > > > directly to vma->anon_name->name and it is used after the call to > > > vma_merge. In the cases when vma_merge merges the original vma and > > > destroys it, this will result in use-after-free bug as shown below: > > > > > > madvise_vma_behavior << passes vma->anon_name->name as name param > > > madvise_update_vma(name) > > > vma_merge > > > __vma_adjust > > > vm_area_free <-- frees the vma > > > replace_vma_anon_name(name) <-- UAF > > > > > > Fix this by raising the name refcount and stabilizing it. Introduce > > > vma_anon_name_{get/put} API for this purpose. > > > > What is the reason that madvise_update_vma uses the naked name rather > > than the encapsulated anon_vma_name? This really just begs for problems. > > The reason for that is the second place it's being used from the prctl syscall: > > prctl_set_vma > madvise_set_anon_name > madvise_vma_anon_name > madvise_update_vma > > In that case the name parameter is not part of any anon_vma_name > struct and therefore is stable. I can add a comment to > madvise_update_vma indicating that the name parameter has to be stable > if that helps. Seems to me it'd simplify things if replace_vma_anon_name() and madvise_vma_anon_name() took a struct anon_vma_name instead of a bare char *. You could construct it in madvise_set_anon_name().