Fix tagged item parsing infinite loop when 32-bit and len=0xFFFFFFF8

diff --git a/NEWS b/NEWS
index 81ae85390e8c0a363b55209e4a78d5ed17580710..50c2131339657a7c0cf6e9666837b3f21227abf1 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -1,3 +1,7 @@
+Version 1.8.2-BETA:
+       Fixed a bug: on 32-bit systems, the library would enter an infinite loop
+       if WIM image metadata was malformed in a very specific way.
+
 Version 1.8.1:
        Fixed a bug in the LZX decompressor: malicious input data could cause
        out of bounds writes to memory (since wimlib v1.2.2).

diff --git a/src/tagged_items.c b/src/tagged_items.c
index e3ba53f496612c7d95e8dabaa12d3512865edca6..1ae227c85f551b6afb65a98aa9c6b694674fb9c3 100644 (file)
--- a/src/tagged_items.c
+++ b/src/tagged_items.c
@@ -44,12 +44,7 @@ struct tagged_item_header {
        le32 tag;
 
        /* Size of the data of this tagged item, in bytes.  This excludes this
-        * header and should be a multiple of 8.
-        *
-        * (Actually, the MS implementation seems to round this up to an 8 byte
-        * boundary when calculating the offset to the next tagged item, but
-        * uses this length unmodified when validating the item.  We might as
-        * well do the same.)  */
+        * header and should be a multiple of 8.  */
        le32 length;
 
        /* Variable length data  */
@@ -90,14 +85,16 @@ inode_get_tagged_item(const struct wim_inode *inode,
 
                hdr = (struct tagged_item_header *)p;
                tag = le32_to_cpu(hdr->tag);
-               len = le32_to_cpu(hdr->length);
+               len = (le32_to_cpu(hdr->length) + 7) & ~7;
 
+               /* Length overflow?  */
+               if (unlikely(len > len_remaining - sizeof(struct tagged_item_header)))
+                       return NULL;
+
+               /* Matches the item we wanted?  */
                if (tag == desired_tag && len >= min_data_len)
                        return hdr->data;
 
-               len = (len + 7) & ~7;
-               if (len_remaining <= sizeof(struct tagged_item_header) + len)
-                       return NULL;
                len_remaining -= sizeof(struct tagged_item_header) + len;
                p += sizeof(struct tagged_item_header) + len;
        }