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fscrypt: destroy keyring after security_sb_delete()

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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: d7e7b9af10 ("fscrypt: stop using keyrings subsystem for fscrypt_master_key")
Cc: stable@vger.kernel.org
Reported-by: syzbot+93e495f6a4f748827c88@syzkaller.appspotmail.com
Link: https://lore.kernel.org/r/00000000000044651705f6ca1e30@google.com
Reviewed-by: Christian Brauner <brauner@kernel.org>
Link: https://lore.kernel.org/r/20230313221231.272498-2-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
This commit is contained in:
Eric Biggers 2023-03-13 15:12:29 -07:00
parent fe15c26ee2
commit ccb820dc7d
1 changed files with 12 additions and 3 deletions
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15
fs/super.c
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@ -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;