diff --git a/fs/ntfs3/fslog.c b/fs/ntfs3/fslog.c
index 847048637dda..2bd8754ef26d 100644
--- a/fs/ntfs3/fslog.c
+++ b/fs/ntfs3/fslog.c
@@ -3598,9 +3598,23 @@ static int do_action(struct ntfs_log *log, struct OPEN_ATTR_ENRTY *oe,
 		}
 
 		e1 = Add2Ptr(e, esize);
-		nsize = esize;
 		used = le32_to_cpu(hdr->used);
 
+		/*
+		 * Reject crafted entries whose e->size makes e + esize
+		 * point past the INDEX_HDR's used boundary.  Without this,
+		 * PtrOffset(e1, hdr + used) underflows to a quasi-infinite
+		 * size_t when fed to the memmove() below.
+		 *
+		 * Also reject esize == 0: memmove(e, e, ...) is a no-op and
+		 * leaves hdr->used unchanged, masking the crafted entry.
+		 */
+		if (!esize || Add2Ptr(e, esize) > Add2Ptr(hdr, used) ||
+		    PtrOffset(e1, Add2Ptr(hdr, used)) < esize)
+			goto dirty_vol;
+
+		nsize = esize;
+
 		memmove(e, e1, PtrOffset(e1, Add2Ptr(hdr, used)));
 
 		hdr->used = cpu_to_le32(used - nsize);