Commit 1823d475 authored Sep 27, 2017 by Eric Biggers Committed by David Howells Oct 18, 2017

KEYS: load key flags and expiry time atomically in key_validate()

In key_validate(), load the flags and expiry time once atomically, since
these can change concurrently if key_validate() is called without the
key semaphore held. And we don't want to get inconsistent results if a
variable is referenced multiple times. For example, key->expiry was
referenced in both 'if (key->expiry)' and in 'if (now.tv_sec >=
key->expiry)', making it theoretically possible to see a spurious
EKEYEXPIRED while the expiration time was being removed, i.e. set to 0.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>

parent 60ff5b2f

security/keys/permission.c

+4 −3

Original line number	Diff line number	Diff line
		@@ -88,7 +88,8 @@ EXPORT_SYMBOL(key_task_permission);
		*/
		int key_validate(const struct key *key)
		{
		unsigned long flags = key->flags;
		unsigned long flags = READ_ONCE(key->flags);
		time_t expiry = READ_ONCE(key->expiry);

		if (flags & (1 << KEY_FLAG_INVALIDATED))
		return -ENOKEY;
		@@ -99,9 +100,9 @@ int key_validate(const struct key *key)
		return -EKEYREVOKED;

		/* check it hasn't expired */
		if (key->expiry) {
		if (expiry) {
		struct timespec now = current_kernel_time();
		if (now.tv_sec >= key->expiry)
		if (now.tv_sec >= expiry)
		return -EKEYEXPIRED;
		}