Commit ccb820dc authored by Eric Biggers's avatar Eric Biggers
Browse files

fscrypt: destroy keyring after security_sb_delete() 



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: d7e7b9af ("fscrypt: stop using keyrings subsystem for fscrypt_master_key")
Cc: stable@vger.kernel.org
Reported-by: default avatar <syzbot+93e495f6a4f748827c88@syzkaller.appspotmail.com>
Link: https://lore.kernel.org/r/00000000000044651705f6ca1e30@google.com


Reviewed-by: default avatarChristian Brauner <brauner@kernel.org>
Link: https://lore.kernel.org/r/20230313221231.272498-2-ebiggers@kernel.org


Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
parent fe15c26e

fs/super.c

+12 −3
Original line number Diff line number Diff line
@@ -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;