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>
diff --git a/security/keys/permission.c b/security/keys/permission.c
index 732cc0b..a72b4dd 100644
--- a/security/keys/permission.c
+++ b/security/keys/permission.c
@@ -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;
}
