Merge branch 'linux-5.6' of git://github.com/skeggsb/linux into drm-fixes

[linux.git] / fs / ubifs / master.c

diff --git a/fs/ubifs/master.c b/fs/ubifs/master.c
index b42a768709c0cd1f771a96b9a09baa5126280503..52a85c01397ef9cbe58aba475cced73831abe2b9 100644 (file)
--- a/fs/ubifs/master.c
+++ b/fs/ubifs/master.c
@@ -48,6 +48,39 @@ int ubifs_compare_master_node(struct ubifs_info *c, void *m1, void *m2)
        return 0;
 }
 
+/* mst_node_check_hash - Check hash of a master node
+ * @c: UBIFS file-system description object
+ * @mst: The master node
+ * @expected: The expected hash of the master node
+ *
+ * This checks the hash of a master node against a given expected hash.
+ * Note that we have two master nodes on a UBIFS image which have different
+ * sequence numbers and consequently different CRCs. To be able to match
+ * both master nodes we exclude the common node header containing the sequence
+ * number and CRC from the hash.
+ *
+ * Returns 0 if the hashes are equal, a negative error code otherwise.
+ */
+static int mst_node_check_hash(const struct ubifs_info *c,
+                              const struct ubifs_mst_node *mst,
+                              const u8 *expected)
+{
+       u8 calc[UBIFS_MAX_HASH_LEN];
+       const void *node = mst;
+
+       SHASH_DESC_ON_STACK(shash, c->hash_tfm);
+
+       shash->tfm = c->hash_tfm;
+
+       crypto_shash_digest(shash, node + sizeof(struct ubifs_ch),
+                           UBIFS_MST_NODE_SZ - sizeof(struct ubifs_ch), calc);
+
+       if (ubifs_check_hash(c, expected, calc))
+               return -EPERM;
+
+       return 0;
+}
+
 /**
  * scan_for_master - search the valid master node.
  * @c: UBIFS file-system description object
@@ -102,14 +135,22 @@ static int scan_for_master(struct ubifs_info *c)
        if (!ubifs_authenticated(c))
                return 0;
 
-       err = ubifs_node_verify_hmac(c, c->mst_node,
-                                    sizeof(struct ubifs_mst_node),
-                                    offsetof(struct ubifs_mst_node, hmac));
-       if (err) {
-               ubifs_err(c, "Failed to verify master node HMAC");
-               return -EPERM;
+       if (ubifs_hmac_zero(c, c->mst_node->hmac)) {
+               err = mst_node_check_hash(c, c->mst_node,
+                                         c->sup_node->hash_mst);
+               if (err)
+                       ubifs_err(c, "Failed to verify master node hash");
+       } else {
+               err = ubifs_node_verify_hmac(c, c->mst_node,
+                                       sizeof(struct ubifs_mst_node),
+                                       offsetof(struct ubifs_mst_node, hmac));
+               if (err)
+                       ubifs_err(c, "Failed to verify master node HMAC");
        }
 
+       if (err)
+               return -EPERM;
+
        return 0;
 
 out: