A few cleanups around symlinks

libcomposefs/lcfs-writer-erofs.c

@@ -1746,7 +1746,7 @@ static struct lcfs_node_s *lcfs_build_node_from_image(struct lcfs_image_data *da
 
 		memcpy(name_buf, tail_data, file_size);
 		name_buf[file_size] = 0;
-		if (lcfs_node_set_payload(node, name_buf) < 0)
+		if (lcfs_node_set_symlink_payload(node, name_buf) < 0)
 			return NULL;
 
 	} else if (type == S_IFREG && file_size != 0 && erofs_inode_is_flat(cino)) {

libcomposefs/lcfs-writer.c

@@ -813,7 +813,7 @@ struct lcfs_node_s *lcfs_load_node_from_file(int dirfd, const char *fname,
 			return NULL;
 
 		target[r] = '\0';
-		r = lcfs_node_set_payload(ret, target);
+		r = lcfs_node_set_symlink_payload(ret, target);
 		if (r < 0)
 			return NULL;
 	}
@@ -917,6 +917,33 @@ int lcfs_node_set_payload(struct lcfs_node_s *node, const char *payload)
 	return 0;
 }
 
+int lcfs_node_set_symlink_payload(struct lcfs_node_s *node, const char *payload)
+{
+	// Caller must have ensured this
+	assert((node->inode.st_mode & S_IFMT) == S_IFLNK);
+	// Symlink target must be non-empty
+	if (payload == NULL || !*payload) {
+		errno = EINVAL;
+		return -1;
+	}
+	// Call the "raw" API for setting payloads, which also verifies
+	// maximum length.
+	if (lcfs_node_set_payload(node, payload) < 0) {
+		return -1;
+	}
+	// We must have set a payload now
+	assert(node->payload);
+	// Historically we accept any arbitrary data in the dumpfile
+	// for the file size for symlink, and end up ignoring it
+	// ultimately when we write the EROFS. However previously
+	// it was pretty confusing as the in-memory node data
+	// could have a bogus size. If somehow the inode state claimed
+	// something else for size, let's always replace it with the symlink
+	// length which is canonical.
+	node->inode.st_size = strlen(node->payload);
+	return 0;
+}
+
 const char *lcfs_node_get_payload(struct lcfs_node_s *node)
 {
 	return node->payload;
@@ -989,6 +1016,15 @@ void lcfs_node_set_mode(struct lcfs_node_s *node, uint32_t mode)
 	node->inode.st_mode = mode;
 }
 
+int lcfs_node_try_set_mode(struct lcfs_node_s *node, uint32_t mode)
+{
+	if (lcfs_validate_mode(mode) < 0) {
+		return -1;
+	}
+	node->inode.st_mode = mode;
+	return 0;
+}
+
 uint32_t lcfs_node_get_uid(struct lcfs_node_s *node)
 {
 	return node->inode.st_uid;

libcomposefs/lcfs-writer.h

@@ -108,6 +108,8 @@ LCFS_EXTERN const char *lcfs_node_get_xattr_name(struct lcfs_node_s *node,
 						 size_t index);
 
 LCFS_EXTERN int lcfs_node_set_payload(struct lcfs_node_s *node, const char *payload);
+LCFS_EXTERN int lcfs_node_set_symlink_payload(struct lcfs_node_s *node,
+					      const char *payload);
 LCFS_EXTERN const char *lcfs_node_get_payload(struct lcfs_node_s *node);
 
 LCFS_EXTERN int lcfs_node_set_content(struct lcfs_node_s *node,
@@ -131,6 +133,7 @@ LCFS_EXTERN struct lcfs_node_s *lcfs_node_get_hardlink_target(struct lcfs_node_s
 LCFS_EXTERN bool lcfs_node_dirp(struct lcfs_node_s *node);
 LCFS_EXTERN uint32_t lcfs_node_get_mode(struct lcfs_node_s *node);
 LCFS_EXTERN void lcfs_node_set_mode(struct lcfs_node_s *node, uint32_t mode);
+LCFS_EXTERN int lcfs_node_try_set_mode(struct lcfs_node_s *node, uint32_t mode);
 LCFS_EXTERN uint32_t lcfs_node_get_uid(struct lcfs_node_s *node);
 LCFS_EXTERN void lcfs_node_set_uid(struct lcfs_node_s *node, uint32_t uid);
 LCFS_EXTERN uint32_t lcfs_node_get_gid(struct lcfs_node_s *node);

tools/mkcomposefs.c

@@ -437,7 +437,10 @@ static char *tree_from_dump_line(dump_info *info, const char *line, size_t line_
 	if (node == NULL) {
 		oom();
 	}
-	lcfs_node_set_mode(node, mode);
+	if (lcfs_node_try_set_mode(node, mode) < 0) {
+		return make_error("Invalid mode %o", (unsigned int)mode);
+	}
+	unsigned int type = mode & S_IFMT;
 
 	err = tree_add_node(info, path, node);
 	if (err)
@@ -507,21 +510,22 @@ static char *tree_from_dump_line(dump_info *info, const char *line, size_t line_
 	if (digest == NULL && err)
 		return err;
 
-	lcfs_node_set_mode(node, mode);
-	lcfs_node_set_size(node, size);
+	if (type != S_IFLNK)
+		lcfs_node_set_size(node, size);
 	lcfs_node_set_nlink(node, nlink);
 	lcfs_node_set_uid(node, uid);
 	lcfs_node_set_gid(node, gid);
 	lcfs_node_set_rdev64(node, rdev);
 	lcfs_node_set_mtime(node, &mtime);
 	// Validate that symlinks are non-empty
-	if ((mode & S_IFMT) == S_IFLNK) {
-		if (payload == NULL) {
-			return make_error("Invalid empty symlink");
+	if (type == S_IFLNK) {
+		if (lcfs_node_set_symlink_payload(node, payload) < 0) {
+			return make_error("Invalid symlink");
 		}
+	} else {
+		if (lcfs_node_set_payload(node, payload) < 0)
+			return make_error("Invalid payload");
 	}
-	if (lcfs_node_set_payload(node, payload) < 0)
-		return make_error("Invalid payload");
 	if (content) {
 		ret = lcfs_node_set_content(node, (uint8_t *)content, size);
 		if (ret < 0)