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fscrypt: check for NULL keyring in fscrypt_put_master_key_activeref()

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It is a bug for fscrypt_put_master_key_activeref() to see a NULL
keyring.  But it used to be possible due to the bug, now fixed, where
fscrypt_destroy_keyring() was called before security_sb_delete().  To be
consistent with how fscrypt_destroy_keyring() uses WARN_ON for the same
issue, WARN and leak the fscrypt_master_key if the keyring is NULL
instead of dereferencing the NULL pointer.

This is a robustness improvement, not a fix.

Link: https://lore.kernel.org/r/20230313221231.272498-4-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
This commit is contained in:
Eric Biggers 2023-03-13 15:12:31 -07:00
parent 43e5f1d592
commit 4bcf6f827a
1 changed files with 2 additions and 0 deletions
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2
fs/crypto/keyring.c
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@ -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);