ata: libata-scsi: bound the ATA passthru sense descriptor writes

When an ATA PASS-THROUGH command to an ATAPI device fails, the sense
buffer holds the device's REQUEST SENSE reply, and
ata_scsi_set_passthru_sense_fields() trusts its additional length
byte, sb[7], when adding the ATA Status Return descriptor.  A faulty
or malicious device can use that to make the kernel read and write
past the 96-byte buffer in three ways:

- scsi_sense_desc_find() is passed sb[7] + 8 as the buffer length, so
  its clamp against sb[7] does nothing and the walk runs off the end.
- A type-9 descriptor found near the end is filled in unchecked.
- A new descriptor at sb[8 + len] needs len + 22 bytes, not len + 14,
  so len 75..82 writes up to 8 bytes past the end.

Reproduced with KASAN under qemu, with the emulated ATAPI REQUEST SENSE
reply patched:

  BUG: KASAN: slab-out-of-bounds in scsi_sense_desc_find+0x1a5/0x210
  BUG: KASAN: slab-out-of-bounds in ata_scsi_qc_complete+0x1a15/0x1a50

Both are gone with this patch, and a valid descriptor is still filled
in.

Fixes: 97981926224a ("ata: libata-scsi: Do not overwrite valid sense data when CK_COND=1")
Cc: stable@vger.kernel.org
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Signed-off-by: Matthias Goergens <matthias.goergens@gmail.com>
Link: https://lore.kernel.org/r/20260923175203.1576825-1-matthias.goergens@gmail.com
Signed-off-by: Niklas Cassel <cassel@kernel.org>

0 files changed, 0 insertions, 0 deletions