Merge 3bb156a556 ("Merge tag 'fsverity-for-linus' of git://git.kernel.org/pub/scm/fs/fsverity/linux") into android-mainline

Steps on the way to 6.6-rc1

Change-Id: I5b478409bb52f4010f4ca61c3aceb025dac43837
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

fs/verity/hash_algs.c

@@ -226,6 +226,14 @@ void __init fsverity_check_hash_algs(void)
 		if (!alg->name)
 			continue;
 
+		/*
+		 * 0 must never be allocated as an FS_VERITY_HASH_ALG_* value,
+		 * as it is reserved for users that use 0 to mean unspecified or
+		 * a default value.  fs/verity/ itself doesn't care and doesn't
+		 * have a default algorithm, but some users make use of this.
+		 */
+		BUG_ON(i == 0);
+
 		BUG_ON(alg->digest_size > FS_VERITY_MAX_DIGEST_SIZE);
 
 		/*

fs/verity/signature.c

@@ -62,6 +62,22 @@ int fsverity_verify_signature(const struct fsverity_info *vi,
 		return 0;
 	}
 
+	if (fsverity_keyring->keys.nr_leaves_on_tree == 0) {
+		/*
+		 * The ".fs-verity" keyring is empty, due to builtin signatures
+		 * being supported by the kernel but not actually being used.
+		 * In this case, verify_pkcs7_signature() would always return an
+		 * error, usually ENOKEY.  It could also be EBADMSG if the
+		 * PKCS#7 is malformed, but that isn't very important to
+		 * distinguish.  So, just skip to ENOKEY to avoid the attack
+		 * surface of the PKCS#7 parser, which would otherwise be
+		 * reachable by any task able to execute FS_IOC_ENABLE_VERITY.
+		 */
+		fsverity_err(inode,
+			     "fs-verity keyring is empty, rejecting signed file!");
+		return -ENOKEY;
+	}
+
 	d = kzalloc(sizeof(*d) + hash_alg->digest_size, GFP_KERNEL);
 	if (!d)
 		return -ENOMEM;