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Mon, 01 Jun 2026 16:36:27 -0700 (PDT) Date: Mon, 1 Jun 2026 18:36:19 -0500 From: Ming Lei To: Hillf Danton Cc: Qu Wenruo , Christoph Hellwig , Damien Le Moal , Tetsuo Handa , Jens Axboe , Bart Van Assche , linux-block , LKML , Andrew Morton , Linus Torvalds , linux-btrfs@vger.kernel.org, David Sterba , linux-fsdevel@vger.kernel.org, Christian Brauner Subject: Re: [PATCH v3] loop: Fix NULL pointer dereference in lo_rw_aio() Message-ID: References: <20260601231731.1403-1-hdanton@sina.com> Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260601231731.1403-1-hdanton@sina.com> On Tue, Jun 02, 2026 at 07:17:30AM +0800, Hillf Danton wrote: > On Mon, 1 Jun 2026 17:14:59 -0500 Ming Lei wrote: > > On Tue, Jun 02, 2026 at 05:51:26AM +0800, Hillf Danton wrote: > > > On OnMon, 1 Jun 2026 10:29:25 -0500 Ming Lei wrote: > > > > syzbot log shows the null-ptr-deref is on WRITE, instead of DISCARD. > > > > > > > > https://syzkaller.appspot.com/bug?extid=cd8a9a308e879a4e2c28 > > > > > > > > Adding WARN_ON(!lo->lo_backing_file) in loop_queue_rq() might capture > > > > this bio submission context if this req isn't issued via wq. > > > > > > > I suspect this makes $.02 sense given the check of Lo_bound upon queuing rq. > > > > Can't lo->lo_state be updated after the check? It is totally lockless... > > > Sounds good hm... do you mean it is UNWISE to not flush the loop workqueue > when closing disk? Quite the opposite, it is wise to not flush wq in __loop_clr_fd(), please see my previous comment. Thanks, Ming