s390/zcrypt: Fix and improve zcrypt reply message verification checks

Add or improve checks related to buffer sizes and reply sizes to the
handling of replies from the crypto cards for CCA, EP11 (AP message
type 6) and ICA (AP type 50) messages. The verification code related
to reply field length was not designed well and thus firmware
deficiencies could lead to unexpected behavior in the zcrypt device
driver. Thus improve the code to more closely inspect especially
length fields at message replies.

Add length validation before accessing reply message structures in
zcrypt_msgtype6_receive(), zcrypt_msgtype6_receive_ep11(), and
zcrypt_msgtype50_receive() to prevent out-of-bounds reads and
potential kernel memory disclosure.

Also rework these three functions to validate reply lengths more
carefully before copying data back into the request buffer. Use size_t
for length calculations, reject inconsistent reply sizes, and add
defensive handling for short invalid replies. For XCRB replies,
validate both reply segments and derive the effective message length
from the covered range instead of trusting only the second segment.

Additionally improve some of the later invoked evaluation functions
which further check the payload. Add comments about length assumptions
and for the type50 processing rework the payload processing completely
with removing a misplaced BUG_ON().

Fixes: 5e55a488c87a ("s390/zcrypt: Separate msgtype implementation from card modules.")
Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Cc: stable@vger.kernel.org
Reviewed-by: Holger Dengler <dengler@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

0 files changed, 0 insertions, 0 deletions