In the Linux kernel, the following vulnerability has been resolved:
dm-integrity: replace forgeable discard filler with a keyed sector marker
The discard-block check in dm_integrity_rw_tag() treats a stored tag
of all 0xf6 bytes (DISCARD_FILLER) as proof a block was discarded and
skips HMAC verification. allow_discards is only accepted in
dm-integrity’s standalone mode. An attacker with raw write access to
the backing device, but without the integrity key, can stamp any block
with an all-0xf6 tag and have it served as authentic.
Add a new “allow_discards_keyed” target argument that marks discarded
blocks with a keyed checksum of (salt || sector) instead, computed by
integrity_discard_checksum().
