CVE-2025-40241: 
Linux Debian vulnerability analysis and mitigation

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

erofs: fix crafted invalid cases for encoded extents

Robert recently reported two corrupted images that can cause system crashes, which are related to the new encoded extents introduced in Linux 6.15:

• The first one [1] has plen != 0 (e.g. plen == 0x2000000) but (plen & Z_EROFS_EXTENT_PLEN_MASK) == 0. It is used to represent special extents such as sparse extents (!EROFS_MAP_MAPPED), but previously only plen == 0 was handled;

• The second one [2] has pa 0xffffffffffdcffed and plen 0xb4000, then "cur [0xfffffffffffff000] += bvec.bv_len [0x1000]" in "} while ((cur += bvec.bv_len) < end);" wraps around, causing an out-of-bound access of pcl->compressed_bvecs[] in z_erofs_submit_queue(). EROFS only supports 48-bit physical block addresses (up to 1EiB for 4k blocks), so add a sanity check to enforce this.