Description: blktrace: debugfs_remove use-after-free
References:
 https://bugzilla.kernel.org/show_bug.cgi?id=205713
 https://syzkaller.appspot.com/bug?extid=903b72a010ad6b7a40f2
 https://lore.kernel.org/lkml/20200206111052.45356-1-yukuai3@huawei.com/
 https://lore.kernel.org/linux-block/20200402000002.7442-1-mcgrof@kernel.org/
Notes:
 bwh> Note that only root can access debugfs by default.
 bwh> Introduced in 4.11-rc1 by commit 6ac93117ab00 "blktrace: use existing
 bwh> disk debugfs directory".
 carnil> Commit landed in 5.7.16, 5.8.2 as well.
Bugs:
upstream: released (5.9-rc1) [bad8e64fb19d3a0de5e564d9a7271c31bd684369]
4.19-upstream-stable: released (4.19.156) [8a78b4c0d6292d32d76b4268b5a33ae089a5d791]
4.9-upstream-stable: N/A "Vulnerability introduced later"
3.16-upstream-stable: ignored "EOL"
sid: released (5.7.17-1)
4.19-buster-security: released (4.19.160-1)
4.9-stretch-security: N/A "Vulnerability introduced later"
3.16-jessie-security: ignored "EOL"