[Devel] [PATCH RHEL7 COMMIT] ploop: possible NULL pointer dereference in ploop_thaw

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-1127.8.2.vz7.151.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-1127.8.2.vz7.151.9
------>
commit 5f6b64fc40675a65e3c9a3f942d499f5d7d3e277
Author: Vasily Averin <vvs at virtuozzo.com>
Date:   Mon Jun 1 13:27:21 2020 +0300

    ploop: possible NULL pointer dereference in ploop_thaw
    
    found by smatch:
    drivers/block/ploop/dev.c:5334 ploop_thaw() error:
     we previously assumed 'bdev' could be null (see line 5318)
    
    Signed-off-by: Vasily Averin <vvs at virtuozzo.com>
    Reviewed-by: Kirill Tkhai <ktkhai at virtuozzo.com>
    Reviewed-by: Konstantin Khorenko <khorenko at virtuozzo.com>
---
 drivers/block/ploop/dev.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/block/ploop/dev.c b/drivers/block/ploop/dev.c
index da124fa50250b..9f0a60d63720d 100644
--- a/drivers/block/ploop/dev.c
+++ b/drivers/block/ploop/dev.c
@@ -5315,7 +5315,7 @@ static int ploop_freeze(struct ploop_device *plo, struct block_device *bdev)
 static int ploop_thaw(struct ploop_device *plo)
 {
 	struct block_device *bdev = plo->frozen_bdev;
-	struct super_block *sb = bdev ? bdev->bd_super : NULL;
+	struct super_block *sb;
 	int err;
 
 	if (!test_bit(PLOOP_S_RUNNING, &plo->state))
@@ -5327,6 +5327,10 @@ static int ploop_thaw(struct ploop_device *plo)
 	if (plo->freeze_state == PLOOP_F_THAWING)
 		return -EBUSY;
 
+	if (!bdev)
+		return -EINVAL;
+	sb = bdev->bd_super;
+
 	plo->frozen_bdev = NULL;
 	plo->freeze_state = PLOOP_F_THAWING;