From: Eric Biggers <ebiggers@xxxxxxxxxx>
fscrypt_destroy_keyring() must be called after all potentially-encrypted
inodes were evicted; otherwise it cannot safely destroy the keyring.
Since inodes that are in-use by the Landlock LSM don't get evicted until
security_sb_delete(), this means that fscrypt_destroy_keyring() must be
called *after* security_sb_delete().
This fixes a WARN_ON followed by a NULL dereference, only possible if
Landlock was being used on encrypted files.
Fixes: d7e7b9af104c ("fscrypt: stop using keyrings subsystem for fscrypt_master_key")
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: syzbot+93e495f6a4f748827c88@xxxxxxxxxxxxxxxxxxxxxxxxx
Link: https://lore.kernel.org/r/00000000000044651705f6ca1e30@xxxxxxxxxx
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
---
fs/super.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/fs/super.c b/fs/super.c
index 84332d5cb817a..04bc62ab7dfea 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -475,13 +475,22 @@ void generic_shutdown_super(struct super_block *sb)
cgroup_writeback_umount();
- /* evict all inodes with zero refcount */
+ /* Evict all inodes with zero refcount. */
evict_inodes(sb);
- /* only nonzero refcount inodes can have marks */
+
+ /*
+ * Clean up and evict any inodes that still have references due
+ * to fsnotify or the security policy.
+ */
fsnotify_sb_delete(sb);
- fscrypt_destroy_keyring(sb);
security_sb_delete(sb);
+ /*
+ * Now that all potentially-encrypted inodes have been evicted,
+ * the fscrypt keyring can be destroyed.
+ */
+ fscrypt_destroy_keyring(sb);
+
if (sb->s_dio_done_wq) {
destroy_workqueue(sb->s_dio_done_wq);
sb->s_dio_done_wq = NULL;
--
2.39.2
