Description: block: Fix use-after-free in blkdev_get()
References:
 https://lkml.org/lkml/2020/6/7/379
Notes:
Bugs:
upstream: released (5.8-rc2) [2d3a8e2deddea6c89961c422ec0c5b851e648c14]
4.19-upstream-stable: released (4.19.130) [49289b1fa5a67011c4010e4e9c801b9d565ce395]
4.9-upstream-stable: released (4.9.229) [a54b15af2b495ed97660a6276710ef36e06ac6c9]
sid: released (5.7.6-1)
4.19-buster-security: released (4.19.131-1)
4.9-stretch-security: released (4.9.240-1)