[PATCH 4.19 157/219] bcache: fix static checker warning in bcache_device_free()

Greg Kroah-Hartman
2019-12-29T17:38:50Z

From: Coly Li <colyli@suse.de>

[ Upstream commit 2d8869518a525c9bce5f5268419df9dfbe3dfdeb ]

Commit cafe56359144 ("bcache: A block layer cache") leads to the
following static checker warning:

./drivers/md/bcache/super.c:770 bcache_device_free()
warn: variable dereferenced before check 'd->disk' (see line 766)

drivers/md/bcache/super.c
762 static void bcache_device_free(struct bcache_device *d)
763 {
764 lockdep_assert_held(&bch_register_lock);
765
766 pr_info("%s stopped", d->disk->disk_name);
^^^^^^^^^
Unchecked dereference.

767
768 if (d->c)
769 bcache_device_detach(d);
770 if (d->disk && d->disk->flags & GENHD_FL_UP)
^^^^^^^
Check too late.

771 del_gendisk(d->disk);
772 if (d->disk && d->disk->queue)
773 blk_cleanup_queue(d->disk->queue);
774 if (d->disk) {
775 ida_simple_remove(&bcache_device_idx,
776 first_minor_to_idx(d->disk->first_minor));
777 put_disk(d->disk);
778 }
779

It is not 100% sure that the gendisk struct of bcache device will always
be there, the warning makes sense when there is problem in block core.

This patch tries to remove the static checking warning by checking
d->disk to avoid NULL pointer deferences.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/md/bcache/super.c | 24 ++++++++++++++++--------
1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 14d381cc6d74..2d60bcdb5b9c 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -747,20 +747,28 @@ static inline int idx_to_first_minor(int idx)

static void bcache_device_free(struct bcache_device *d)
{
+ struct gendisk *disk = d->disk;
+
lockdep_assert_held(&bch_register_lock);

- pr_info("%s stopped", d->disk->disk_name);
+ if (disk)
+ pr_info("%s stopped", disk->disk_name);
+ else
+ pr_err("bcache device (NULL gendisk) stopped");

if (d->c)
bcache_device_detach(d);
- if (d->disk && d->disk->flags & GENHD_FL_UP)
- del_gendisk(d->disk);
- if (d->disk && d->disk->queue)
- blk_cleanup_queue(d->disk->queue);
- if (d->disk) {
+
+ if (disk) {
+ if (disk->flags & GENHD_FL_UP)
+ del_gendisk(disk);
+
+ if (disk->queue)
+ blk_cleanup_queue(disk->queue);
+
ida_simple_remove(&bcache_device_idx,
- first_minor_to_idx(d->disk->first_minor));
- put_disk(d->disk);
+ first_minor_to_idx(disk->first_minor));
+ put_disk(disk);
}

bioset_exit(&d->bio_split);
--
2.20.1