mount: Fix ioctl to not use GNU C extension

Signed-off-by: Colin Walters <[email protected]>

libcomposefs/lcfs-mount.c

@@ -221,23 +221,20 @@ static errint_t lcfs_validate_mount_options(struct lcfs_mount_state_s *state)
 
 static errint_t lcfs_validate_verity_fd(struct lcfs_mount_state_s *state)
 {
-	struct {
-		struct fsverity_digest fsv;
-		char buf[MAX_DIGEST_SIZE];
-	} buf;
+	char buf[sizeof(struct fsverity_digest) + MAX_DIGEST_SIZE];
+	struct fsverity_digest *fsv = (struct fsverity_digest *)&buf;
 	int res;
 
 	if (state->expected_digest_len != 0) {
-		buf.fsv.digest_size = MAX_DIGEST_SIZE;
-		res = ioctl(state->fd, FS_IOC_MEASURE_VERITY, &buf.fsv);
+		fsv->digest_size = MAX_DIGEST_SIZE;
+		res = ioctl(state->fd, FS_IOC_MEASURE_VERITY, fsv);
 		if (res == -1) {
 			if (errno == ENODATA || errno == EOPNOTSUPP || errno == ENOTTY)
 				return -ENOVERITY;
 			return -errno;
 		}
-		if (buf.fsv.digest_size != state->expected_digest_len ||
-		    memcmp(state->expected_digest, buf.fsv.digest,
-			   buf.fsv.digest_size) != 0)
+		if (fsv->digest_size != state->expected_digest_len ||
+		    memcmp(state->expected_digest, fsv->digest, fsv->digest_size) != 0)
 			return -EWRONGVERITY;
 	}