KEYS: Fix race between updating and finding a negative key

[mirror_ubuntu-hirsute-kernel.git] / include / linux / key.h

diff --git a/include/linux/key.h b/include/linux/key.h
index e315e16b6ff8a0aaade2552ee404d35e27da5570..8a15cabe928d0ee282742f0c44be26e7af01851d 100644 (file)
--- a/include/linux/key.h
+++ b/include/linux/key.h
@@ -138,6 +138,11 @@ struct key_restriction {
        struct key_type *keytype;
 };
 
+enum key_state {
+       KEY_IS_UNINSTANTIATED,
+       KEY_IS_POSITIVE,                /* Positively instantiated */
+};
+
 /*****************************************************************************/
 /*
  * authentication token / access credential / keyring
@@ -169,6 +174,7 @@ struct key {
                                                 * - may not match RCU dereferenced payload
                                                 * - payload should contain own length
                                                 */
+       short                   state;          /* Key state (+) or rejection error (-) */
 
 #ifdef KEY_DEBUGGING
        unsigned                magic;
@@ -176,18 +182,16 @@ struct key {
 #endif
 
        unsigned long           flags;          /* status flags (change with bitops) */
-#define KEY_FLAG_INSTANTIATED  0       /* set if key has been instantiated */
-#define KEY_FLAG_DEAD          1       /* set if key type has been deleted */
-#define KEY_FLAG_REVOKED       2       /* set if key had been revoked */
-#define KEY_FLAG_IN_QUOTA      3       /* set if key consumes quota */
-#define KEY_FLAG_USER_CONSTRUCT        4       /* set if key is being constructed in userspace */
-#define KEY_FLAG_NEGATIVE      5       /* set if key is negative */
-#define KEY_FLAG_ROOT_CAN_CLEAR        6       /* set if key can be cleared by root without permission */
-#define KEY_FLAG_INVALIDATED   7       /* set if key has been invalidated */
-#define KEY_FLAG_BUILTIN       8       /* set if key is built in to the kernel */
-#define KEY_FLAG_ROOT_CAN_INVAL        9       /* set if key can be invalidated by root without permission */
-#define KEY_FLAG_KEEP          10      /* set if key should not be removed */
-#define KEY_FLAG_UID_KEYRING   11      /* set if key is a user or user session keyring */
+#define KEY_FLAG_DEAD          0       /* set if key type has been deleted */
+#define KEY_FLAG_REVOKED       1       /* set if key had been revoked */
+#define KEY_FLAG_IN_QUOTA      2       /* set if key consumes quota */
+#define KEY_FLAG_USER_CONSTRUCT        3       /* set if key is being constructed in userspace */
+#define KEY_FLAG_ROOT_CAN_CLEAR        4       /* set if key can be cleared by root without permission */
+#define KEY_FLAG_INVALIDATED   5       /* set if key has been invalidated */
+#define KEY_FLAG_BUILTIN       6       /* set if key is built in to the kernel */
+#define KEY_FLAG_ROOT_CAN_INVAL        7       /* set if key can be invalidated by root without permission */
+#define KEY_FLAG_KEEP          8       /* set if key should not be removed */
+#define KEY_FLAG_UID_KEYRING   9       /* set if key is a user or user session keyring */
 
        /* the key type and key description string
         * - the desc is used to match a key against search criteria
@@ -213,7 +217,6 @@ struct key {
                        struct list_head name_link;
                        struct assoc_array keys;
                };
-               int reject_error;
        };
 
        /* This is set on a keyring to restrict the addition of a link to a key
@@ -353,17 +356,27 @@ extern void key_set_timeout(struct key *, unsigned);
 #define        KEY_NEED_SETATTR 0x20   /* Require permission to change attributes */
 #define        KEY_NEED_ALL    0x3f    /* All the above permissions */
 
+static inline short key_read_state(const struct key *key)
+{
+       /* Barrier versus mark_key_instantiated(). */
+       return smp_load_acquire(&key->state);
+}
+
 /**
- * key_is_instantiated - Determine if a key has been positively instantiated
+ * key_is_positive - Determine if a key has been positively instantiated
  * @key: The key to check.
  *
  * Return true if the specified key has been positively instantiated, false
  * otherwise.
  */
-static inline bool key_is_instantiated(const struct key *key)
+static inline bool key_is_positive(const struct key *key)
+{
+       return key_read_state(key) == KEY_IS_POSITIVE;
+}
+
+static inline bool key_is_negative(const struct key *key)
 {
-       return test_bit(KEY_FLAG_INSTANTIATED, &key->flags) &&
-               !test_bit(KEY_FLAG_NEGATIVE, &key->flags);
+       return key_read_state(key) < 0;
 }
 
 #define dereference_key_rcu(KEY)                                       \