libfstree: guard against link count and inode number overflow

If the hard link counter or the inode number counter overflow the
maximum representable value (for SquashFS 16 bit and 32 bit
respecitively), abort with an error message.

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

1 files changed, 11 insertions, 2 deletions

diff --git a/lib/fstree/mknode.c b/lib/fstree/mknode.c
index 4353b74..f836c67 100644
--- a/lib/fstree/mknode.c
+++ b/lib/fstree/mknode.c
@@ -70,10 +70,19 @@ tree_node_t *fstree_mknode(tree_node_t *parent, const char *name,
 	case S_IFDIR:
 		n->link_count = 2;
 		break;
+	default:
+		break;
 	}
 
-	if (parent != NULL)
-		parent->link_count += 1;
+	if (parent != NULL) {
+		if (parent->link_count == 0x0FFFF) {
+			free(n);
+			errno = EMLINK;
+			return NULL;
+		}
+
+		parent->link_count++;
+	}
 
 	return n;
 }