From: Harald Freudenberger freude@linux.ibm.com
commit 4cfca532ddc3474b3fc42592d0e4237544344b1a upstream.
The length information for available buffer space for CCA replies is covered with two fields in the T6 header prepended on each CCA reply: fromcardlen1 and fromcardlen2. The sum of these both values must not exceed the AP bus limit for this card (24KB for CEX8, 12KB CEX7 and older) minus the always present headers.
The current code adjusted the fromcardlen2 value in case of exceeding the AP bus limit when there was a non-zero value given from userspace. Some tests now showed that this was the wrong assumption. Instead the userspace value given for this field should always be trusted and if the sum of the two fields exceeds the AP bus limit for this card the first field fromcardlen1 should be adjusted instead.
So now the calculation is done with this new insight in mind. Also some additional checks for overflow have been introduced and some comments to provide some documentation for future maintainers of this complicated calculation code.
Furthermore the 128 bytes of fix overhead which is used in the current code is not correct. Investigations showed that for a reply always the same two header structs are prepended before a possible payload. So this is also fixed with this patch.
Signed-off-by: Harald Freudenberger freude@linux.ibm.com Reviewed-by: Holger Dengler dengler@linux.ibm.com Cc: stable@vger.kernel.org Signed-off-by: Heiko Carstens hca@linux.ibm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/s390/crypto/zcrypt_msgtype6.c | 33 +++++++++++++++++++++++---------- 1 file changed, 23 insertions(+), 10 deletions(-)
--- a/drivers/s390/crypto/zcrypt_msgtype6.c +++ b/drivers/s390/crypto/zcrypt_msgtype6.c @@ -1111,23 +1111,36 @@ static long zcrypt_msgtype6_send_cprb(bo struct ica_xcRB *xcrb, struct ap_message *ap_msg) { - int rc; struct response_type *rtype = ap_msg->private; struct { struct type6_hdr hdr; struct CPRBX cprbx; /* ... more data blocks ... */ } __packed * msg = ap_msg->msg; + unsigned int max_payload_size; + int rc, delta;
- /* - * Set the queue's reply buffer length minus 128 byte padding - * as reply limit for the card firmware. - */ - msg->hdr.fromcardlen1 = min_t(unsigned int, msg->hdr.fromcardlen1, - zq->reply.bufsize - 128); - if (msg->hdr.fromcardlen2) - msg->hdr.fromcardlen2 = - zq->reply.bufsize - msg->hdr.fromcardlen1 - 128; + /* calculate maximum payload for this card and msg type */ + max_payload_size = zq->reply.bufsize - sizeof(struct type86_fmt2_msg); + + /* limit each of the two from fields to the maximum payload size */ + msg->hdr.fromcardlen1 = min(msg->hdr.fromcardlen1, max_payload_size); + msg->hdr.fromcardlen2 = min(msg->hdr.fromcardlen2, max_payload_size); + + /* calculate delta if the sum of both exceeds max payload size */ + delta = msg->hdr.fromcardlen1 + msg->hdr.fromcardlen2 + - max_payload_size; + if (delta > 0) { + /* + * Sum exceeds maximum payload size, prune fromcardlen1 + * (always trust fromcardlen2) + */ + if (delta > msg->hdr.fromcardlen1) { + rc = -EINVAL; + goto out; + } + msg->hdr.fromcardlen1 -= delta; + }
init_completion(&rtype->work); rc = ap_queue_message(zq->queue, ap_msg);