On 14/07/2023 16:36, Harald Freudenberger wrote:
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 wo fields exceeds the AP bus limit for this card the first
typo: two
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. Investications showed
typo: Investigations
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 Cc: stable@vger.kernel.org
With the typos fixed and the changes below Reviewed-by: Holger Dengler dengler@linux.ibm.com
drivers/s390/crypto/zcrypt_msgtype6.c | 45 ++++++++++++++++++++------- 1 file changed, 33 insertions(+), 12 deletions(-)
diff --git a/drivers/s390/crypto/zcrypt_msgtype6.c b/drivers/s390/crypto/zcrypt_msgtype6.c index 247f0ad38362..5ac110669327 100644 --- a/drivers/s390/crypto/zcrypt_msgtype6.c +++ b/drivers/s390/crypto/zcrypt_msgtype6.c @@ -551,6 +551,12 @@ static int xcrb_msg_to_type6_ep11cprb_msgx(bool userspace, struct ap_message *ap
- Returns 0 on success or -EINVAL, -EFAULT, -EAGAIN in case of an error.
*/ +struct type86_reply_hdrs {
- struct type86_hdr hdr;
- struct type86_fmt2_ext fmt2;
- /* ... payload may follow ... */
+} __packed;
There is already a `struct type86_fmt2_msg` in this file (line 329 ff.).
struct type86x_reply { struct type86_hdr hdr; struct type86_fmt2_ext fmt2; @@ -1101,23 +1107,38 @@ static long zcrypt_msgtype6_send_cprb(bool userspace, struct zcrypt_queue *zq, struct ica_xcRB *xcrb, struct ap_message *ap_msg) {
- int rc;
- unsigned int reply_bufsize_minus_headers =
zq->reply.bufsize - sizeof(struct type86_reply_hdrs);
I don't like this variable name. What about `max_payload_size`?
struct response_type *rtype = ap_msg->private; struct { struct type6_hdr hdr; struct CPRBX cprbx; /* ... more data blocks ... */ } __packed * msg = ap_msg->msg;
- /*
* 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;
- int rc, delta;
- /* limit each of the two from fields to AP bus limit - headers */
I would also use "maximal payload size" here. /* limit each of the two from fields to the maximum payload size */
- msg->hdr.fromcardlen1 = min_t(unsigned int,
msg->hdr.fromcardlen1,reply_bufsize_minus_headers);- msg->hdr.fromcardlen2 = min_t(unsigned int,
msg->hdr.fromcardlen2,reply_bufsize_minus_headers);- /* calculate delta if the sum of both exceeds AP bus limit - headers */
dito: /* calculate delta if the sum of both exceeds the maximum payload size */
- delta = msg->hdr.fromcardlen1 + msg->hdr.fromcardlen2
- reply_bufsize_minus_headers;- if (delta > 0) {
/** Sum exceeds AP bus limit - headers, prune fromcardlen1
dito: * Sum exceeds the 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); @@ -1240,7 +1261,7 @@ static long zcrypt_msgtype6_send_ep11_cprb(bool userspace, struct zcrypt_queue * * as reply limit for the card firmware. */ msg->hdr.fromcardlen1 = zq->reply.bufsize -
sizeof(struct type86_hdr) - sizeof(struct type86_fmt2_ext);
sizeof(struct type86_reply_hdrs);init_completion(&rtype->work); rc = ap_queue_message(zq->queue, ap_msg);