Commit 94c4554b authored Sep 25, 2015 by David Howells

KEYS: Fix race between key destruction and finding a keyring by name



There appears to be a race between:

 (1) key_gc_unused_keys() which frees key->security and then calls
     keyring_destroy() to unlink the name from the name list

 (2) find_keyring_by_name() which calls key_permission(), thus accessing
     key->security, on a key before checking to see whether the key usage is 0
     (ie. the key is dead and might be cleaned up).

Fix this by calling ->destroy() before cleaning up the core key data -
including key->security.

Reported-by: Petr Matousek <pmatouse@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>

parent ced255c0

security/keys/gc.c

+4 −4

Original line number	Diff line number	Diff line
		@@ -134,6 +134,10 @@ static noinline void key_gc_unused_keys(struct list_head *keys)
		kdebug("- %u", key->serial);
		key_check(key);

		/* Throw away the key data */
		if (key->type->destroy)
		key->type->destroy(key);

		security_key_free(key);

		/* deal with the user's key tracking and quota */
		@@ -148,10 +152,6 @@ static noinline void key_gc_unused_keys(struct list_head *keys)
		if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
		atomic_dec(&key->user->nikeys);

		/* now throw away the key memory */
		if (key->type->destroy)
		key->type->destroy(key);

		key_user_put(key->user);

		kfree(key->description);