Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S937525AbdCJNhI (ORCPT ); Fri, 10 Mar 2017 08:37:08 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:43645 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934338AbdCJLw2 (ORCPT ); Fri, 10 Mar 2017 06:52:28 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Christoph Hellwig" , "Linus Torvalds" , "Dmitry Vyukov" , "Al Viro" , "Al Viro" Date: Fri, 10 Mar 2017 11:46:23 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 307/370] Fix missing sanity check in /dev/sg In-Reply-To: X-SA-Exim-Connect-IP: 82.70.136.246 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1407 Lines: 44 3.16.42-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Al Viro commit 137d01df511b3afe1f05499aea05f3bafc0fb221 upstream. What happens is that a write to /dev/sg is given a request with non-zero ->iovec_count combined with zero ->dxfer_len. Or with ->dxferp pointing to an array full of empty iovecs. Having write permission to /dev/sg shouldn't be equivalent to the ability to trigger BUG_ON() while holding spinlocks... Found by Dmitry Vyukov and syzkaller. [ The BUG_ON() got changed to a WARN_ON_ONCE(), but this fixes the underlying issue. - Linus ] Signed-off-by: Al Viro Reported-by: Dmitry Vyukov Reviewed-by: Christoph Hellwig Signed-off-by: Linus Torvalds [bwh: Backported to 3.16: we're not using iov_iter, but can check the byte length after truncation] Signed-off-by: Ben Hutchings --- drivers/scsi/sg.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/drivers/scsi/sg.c +++ b/drivers/scsi/sg.c @@ -1716,6 +1716,10 @@ static int sg_start_req(Sg_request *srp, iov_count = iov_shorten(iov, iov_count, hp->dxfer_len); len = hp->dxfer_len; } + if (len == 0) { + kfree(iov); + return -EINVAL; + } res = blk_rq_map_user_iov(q, rq, md, (struct sg_iovec *)iov, iov_count,