From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl0-f67.google.com ([209.85.160.67]:34740 "EHLO mail-pl0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750962AbeDFQ5M (ORCPT ); Fri, 6 Apr 2018 12:57:12 -0400 Received: by mail-pl0-f67.google.com with SMTP id y12-v6so882369plt.1 for ; Fri, 06 Apr 2018 09:57:12 -0700 (PDT) From: Omar Sandoval To: linux-block@vger.kernel.org Cc: Jens Axboe , kernel-team@fb.com, Tetsuo Handa , Dmitry Vyukov Subject: [PATCH] loop: fix LOOP_GET_STATUS lock imbalance Date: Fri, 6 Apr 2018 09:57:03 -0700 Message-Id: <6bee3eddc24ef5525ca12efb023e66b2503cb178.1523033157.git.osandov@fb.com> Sender: linux-block-owner@vger.kernel.org List-Id: linux-block@vger.kernel.org From: Omar Sandoval 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 --- Based on Linus' tree. drivers/block/loop.c | 33 ++++++++++++++++++--------------- 1 file changed, 18 insertions(+), 15 deletions(-) diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 264abaaff662..9b476fd2bc41 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -1283,12 +1283,13 @@ 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))) @@ -1300,12 +1301,13 @@ loop_get_status_old(struct loop_device *lo, struct loop_info __user *arg) { 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; @@ -1529,12 +1531,13 @@ loop_get_status_compat(struct loop_device *lo, 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; -- 2.17.0