From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.99]:50638 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1031112AbeEXKCo (ORCPT ); Thu, 24 May 2018 06:02:44 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, syzbot+31e8daa8b3fc129e75f2@syzkaller.appspotmail.com, Omar Sandoval , Jens Axboe Subject: [PATCH 4.16 086/161] loop: fix LOOP_GET_STATUS lock imbalance Date: Thu, 24 May 2018 11:38:31 +0200 Message-Id: <20180524093028.748525266@linuxfoundation.org> In-Reply-To: <20180524093018.331893860@linuxfoundation.org> References: <20180524093018.331893860@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.16-stable review patch. If anyone has any objections, please let me know. ------------------ From: Omar Sandoval commit bdac616db9bbadb90b7d6a406144571015e138f7 upstream. Commit 2d1d4c1e591f made loop_get_status() drop lo_ctx_mutex before returning, but the loop_get_status_old(), loop_get_status64(), and loop_get_status_compat() wrappers don't call loop_get_status() if the passed argument is NULL. The callers expect that the lock is dropped, so make sure we drop it in that case, too. Reported-by: syzbot+31e8daa8b3fc129e75f2@syzkaller.appspotmail.com Fixes: 2d1d4c1e591f ("loop: don't call into filesystem while holding lo_ctl_mutex") Signed-off-by: Omar Sandoval Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- drivers/block/loop.c | 33 ++++++++++++++++++--------------- 1 file changed, 18 insertions(+), 15 deletions(-) --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -1287,12 +1287,13 @@ static int loop_get_status_old(struct loop_device *lo, struct loop_info __user *arg) { struct loop_info info; struct loop_info64 info64; - int err = 0; + int err; - if (!arg) - err = -EINVAL; - if (!err) - err = loop_get_status(lo, &info64); + if (!arg) { + mutex_unlock(&lo->lo_ctl_mutex); + return -EINVAL; + } + err = loop_get_status(lo, &info64); if (!err) err = loop_info64_to_old(&info64, &info); if (!err && copy_to_user(arg, &info, sizeof(info))) @@ -1304,12 +1305,13 @@ loop_get_status_old(struct loop_device * static int loop_get_status64(struct loop_device *lo, struct loop_info64 __user *arg) { struct loop_info64 info64; - int err = 0; + int err; - if (!arg) - err = -EINVAL; - if (!err) - err = loop_get_status(lo, &info64); + if (!arg) { + mutex_unlock(&lo->lo_ctl_mutex); + return -EINVAL; + } + err = loop_get_status(lo, &info64); if (!err && copy_to_user(arg, &info64, sizeof(info64))) err = -EFAULT; @@ -1530,12 +1532,13 @@ loop_get_status_compat(struct loop_devic struct compat_loop_info __user *arg) { struct loop_info64 info64; - int err = 0; + int err; - if (!arg) - err = -EINVAL; - if (!err) - err = loop_get_status(lo, &info64); + if (!arg) { + mutex_unlock(&lo->lo_ctl_mutex); + return -EINVAL; + } + err = loop_get_status(lo, &info64); if (!err) err = loop_info64_to_compat(&info64, arg); return err;