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fscrypt fixes for v6.3-rc4 

Fix a bug where when a filesystem was being unmounted, the fscrypt
 keyring was destroyed before inodes have been released by the Landlock
 LSM.  This bug was found by syzbot.
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Merge tag 'fscrypt-for-linus' of git://git.kernel.org/pub/scm/fs/fscrypt/linux

Pull fscrypt fix from Eric Biggers:
 "Fix a bug where when a filesystem was being unmounted, the fscrypt
  keyring was destroyed before inodes have been released by the Landlock
  LSM.

  This bug was found by syzbot"

* tag 'fscrypt-for-linus' of git://git.kernel.org/pub/scm/fs/fscrypt/linux:
  fscrypt: check for NULL keyring in fscrypt_put_master_key_activeref()
  fscrypt: improve fscrypt_destroy_keyring() documentation
  fscrypt: destroy keyring after security_sb_delete()
This commit is contained in:
Linus Torvalds 2023-03-20 15:12:55 -07:00
parent 7d31677bb7 4bcf6f827a
commit 4f1e308df8
2 changed files with 25 additions and 13 deletions
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23
fs/crypto/keyring.c
View File

@ -92,6 +92,8 @@ void fscrypt_put_master_key_activeref(struct super_block *sb,
* destroying any subkeys embedded in it.
*/
if (WARN_ON(!sb->s_master_keys))
return;
spin_lock(&sb->s_master_keys->lock);
hlist_del_rcu(&mk->mk_node);
spin_unlock(&sb->s_master_keys->lock);
@ -207,10 +209,11 @@ static int allocate_filesystem_keyring(struct super_block *sb)
* Release all encryption keys that have been added to the filesystem, along
* with the keyring that contains them.
*
* This is called at unmount time. The filesystem's underlying block device(s)
* are still available at this time; this is important because after user file
* accesses have been allowed, this function may need to evict keys from the
* keyslots of an inline crypto engine, which requires the block device(s).
* This is called at unmount time, after all potentially-encrypted inodes have
* been evicted. The filesystem's underlying block device(s) are still
* available at this time; this is important because after user file accesses
* have been allowed, this function may need to evict keys from the keyslots of
* an inline crypto engine, which requires the block device(s).
*/
void fscrypt_destroy_keyring(struct super_block *sb)
{
@ -227,12 +230,12 @@ void fscrypt_destroy_keyring(struct super_block *sb)
hlist_for_each_entry_safe(mk, tmp, bucket, mk_node) {
/*
* Since all inodes were already evicted, every key
* remaining in the keyring should have an empty inode
* list, and should only still be in the keyring due to
* the single active ref associated with ->mk_secret.
* There should be no structural refs beyond the one
* associated with the active ref.
* Since all potentially-encrypted inodes were already
* evicted, every key remaining in the keyring should
* have an empty inode list, and should only still be in
* the keyring due to the single active ref associated
* with ->mk_secret. There should be no structural refs
* beyond the one associated with the active ref.
*/
WARN_ON(refcount_read(&mk->mk_active_refs) != 1);
WARN_ON(refcount_read(&mk->mk_struct_refs) != 1);

15
fs/super.c
View File

@ -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;