In the Linux kernel, the following vulnerability has been resolved: udf: validate VAT header...

In the Linux kernel, the following vulnerability has been resolved:

udf: validate VAT header length against the VAT inode size

udf_load_vat() takes the virtual partition's start offset straight from the on-disk VAT 2.0 header without checking it against the VAT inode size:

map->s_type_specific.s_virtual.s_start_offset =
	le16_to_cpu(vat20->lengthHeader);
map->s_type_specific.s_virtual.s_num_entries =
	(sbi->s_vat_inode->i_size -
		map->s_type_specific.s_virtual.s_start_offset) >> 2;

lengthHeader is a fully attacker-controlled 16-bit value. If it exceeds the VAT inode size, the s_num_entries subtraction underflows to a huge count, which defeats the "block > s_num_entries" bound in udf_get_pblock_virt15(); and on the ICB-inline path that function reads

((__le32 *)(iinfo->i_data + s_start_offset))[block]

so a large s_start_offset indexes past the inode's in-ICB data. Mounting a crafted UDF image with a virtual (VAT) partition then triggers an out-of-bounds read.

Reject a VAT whose header length does not leave room for at least one entry within the VAT inode.