CVE-2026-31449

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

ext4: validate p_idx bounds in ext4_ext_correct_indexes

ext4_ext_correct_indexes() walks up the extent tree correcting

index entries when the first extent in a leaf is modified. Before

accessing path[k].p_idx->ei_block, there is no validation that

p_idx falls within the valid range of index entries for that

level.

If the on-disk extent header contains a corrupted or crafted

eh_entries value, p_idx can point past the end of the allocated

buffer, causing a slab-out-of-bounds read.

Fix this by validating path[k].p_idx against EXT_LAST_INDEX() at

both access sites: before the while loop and inside it. Return

-EFSCORRUPTED if the index pointer is out of range, consistent

with how other bounds violations are handled in the ext4 extent

tree code.