thunderbolt: Bound root directory content to block size

__tb_property_parse_dir() does not check that content_offset +
content_len fits within block_len for the root directory case.
When rootdir->length equals or exceeds block_len - 2, the entry
loop reads past the allocated property block.

Add a bounds check after computing content_offset and content_len
to reject directories whose content extends past the block.

Fixes: cdae7c07e3 ("thunderbolt: Add support for XDomain properties")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-4-7
Signed-off-by: Michael Bommarito <michael.bommarito@gmail.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

drivers/thunderbolt/property.c

@@ -187,6 +187,10 @@ static struct tb_property_dir *__tb_property_parse_dir(const u32 *block,
 	if (is_root) {
 		content_offset = dir_offset + 2;
 		content_len = dir_len;
+		if (content_offset + content_len > block_len) {
+			tb_property_free_dir(dir);
+			return NULL;
+		}
 	} else {
 		if (dir_len < 4) {
 			tb_property_free_dir(dir);