Description
In the Linux kernel, the following vulnerability has been resolved: vfs: Don't leak disconnected dentries on umount When user calls open_by_handle_at() on some inode that is not cached, we will create disconnected dentry for it. If such dentry is a directory, exportfs_decode_fh_raw() will then try to connect this dentry to the dentry tree through reconnect_path(). It may happen for various reasons (such as corrupted fs or race with rename) that the call to lookup_one_unlocked() in reconnect_one() will fail to find the dentry we are trying to reconnect and instead create a new dentry under the parent. Now this dentry will not be marked as disconnected although the parent still may well be disconnected (at least in case this inconsistency happened because the fs is corrupted and .. doesn't point to the real parent directory). This creates inconsistency in disconnected flags but AFAICS it was mostly harmless. At least until commit f1ee616214cb ("VFS: don't keep disconnected dentries on d_anon") which removed adding of most disconnected dentries to sb->s_anon list. Thus after this commit cleanup of disconnected dentries implicitely relies on the fact that dput() will immediately reclaim such dentries. However when some leaf dentry isn't marked as disconnected, as in the scenario described above, the reclaim doesn't happen and the dentries are "leaked". Memory reclaim can eventually reclaim them but otherwise they stay in memory and if umount comes first, we hit infamous "Busy inodes after unmount" bug. Make sure all dentries created under a disconnected parent are marked as disconnected as well.
Product status
f1ee616214cb22410e939d963bbb2349c2570f02 (git) before b5abafd0aa8d7bcb935c8f91e4cfc2f2820759e4
f1ee616214cb22410e939d963bbb2349c2570f02 (git) before 20863bb7fbb016379f8227122edfabc5c799bc79
f1ee616214cb22410e939d963bbb2349c2570f02 (git) before 8004d4b8cbf1bd68a23c160d57287e177c82cc69
f1ee616214cb22410e939d963bbb2349c2570f02 (git) before 7e0c8aaf4e28918abded547a5147c7d52c4af7d2
f1ee616214cb22410e939d963bbb2349c2570f02 (git) before cebfbf40056a4d858b2a3ca59a69936d599bd209
f1ee616214cb22410e939d963bbb2349c2570f02 (git) before 620f3b0ede9c5cb4976cd0457d0b04ad551e5d6b
f1ee616214cb22410e939d963bbb2349c2570f02 (git) before eadc49999fa994d6fbd70c332bd5d5051cc42261
f1ee616214cb22410e939d963bbb2349c2570f02 (git) before 56094ad3eaa21e6621396cc33811d8f72847a834
4.16
Any version before 4.16
5.4.301 (semver)
5.10.246 (semver)
5.15.196 (semver)
6.1.158 (semver)
6.6.114 (semver)
6.12.55 (semver)
6.17.5 (semver)
6.18-rc2 (original_commit_for_fix)
References
git.kernel.org/...c/b5abafd0aa8d7bcb935c8f91e4cfc2f2820759e4
git.kernel.org/...c/20863bb7fbb016379f8227122edfabc5c799bc79
git.kernel.org/...c/8004d4b8cbf1bd68a23c160d57287e177c82cc69
git.kernel.org/...c/7e0c8aaf4e28918abded547a5147c7d52c4af7d2
git.kernel.org/...c/cebfbf40056a4d858b2a3ca59a69936d599bd209
git.kernel.org/...c/620f3b0ede9c5cb4976cd0457d0b04ad551e5d6b
git.kernel.org/...c/eadc49999fa994d6fbd70c332bd5d5051cc42261
git.kernel.org/...c/56094ad3eaa21e6621396cc33811d8f72847a834
