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drbd: detect modification of in-flight buffers 

With data-integrity digest enabled, double-check on the sending side
for modifications by upper layers of buffers under write back,
so we can tell it appart from corruption on the "wire".

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
This commit is contained in:
Lars Ellenberg 2010-11-10 10:36:52 +01:00 committed by Philipp Reisner
parent 5f9915bbb8
commit 470be44ab1
2 changed files with 29 additions and 2 deletions
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28
drivers/block/drbd/drbd_main.c
View File

@ -2537,10 +2537,36 @@ int drbd_send_dblock(struct drbd_conf *mdev, struct drbd_request *req)
ok = drbd_send(mdev, mdev->data.socket, dgb, dgs, 0);
}
if (ok) {
if (mdev->net_conf->wire_protocol == DRBD_PROT_A)
/* For protocol A, we have to memcpy the payload into
* socket buffers, as we may complete right away
* as soon as we handed it over to tcp, at which point the data
* pages may become invalid.
*
* For data-integrity enabled, we copy it as well, so we can be
* sure that even if the bio pages may still be modified, it
* won't change the data on the wire, thus if the digest checks
* out ok after sending on this side, but does not fit on the
* receiving side, we sure have detected corruption elsewhere.
*/
if (mdev->net_conf->wire_protocol == DRBD_PROT_A || dgs)
ok = _drbd_send_bio(mdev, req->master_bio);
else
ok = _drbd_send_zc_bio(mdev, req->master_bio);
/* double check digest, sometimes buffers have been modified in flight. */
if (dgs > 0 && dgs <= 64) {
/* 64 byte, 512 bit, is the larges digest size
* currently supported in kernel crypto. */
unsigned char digest[64];
drbd_csum_bio(mdev, mdev->integrity_w_tfm, req->master_bio, digest);
if (memcmp(mdev->int_dig_out, digest, dgs)) {
dev_warn(DEV,
"Digest mismatch, buffer modified by upper layers during write: %llus +%u\n",
(unsigned long long)req->sector, req->size);
}
} /* else if (dgs > 64) {
... Be noisy about digest too large ...
} */
}
drbd_put_data_sock(mdev);

3
drivers/block/drbd/drbd_receiver.c
View File

@ -1281,7 +1281,8 @@ read_in_block(struct drbd_conf *mdev, u64 id, sector_t sector, int data_size) __
if (dgs) {
drbd_csum_ee(mdev, mdev->integrity_r_tfm, e, dig_vv);
if (memcmp(dig_in, dig_vv, dgs)) {
dev_err(DEV, "Digest integrity check FAILED.\n");
dev_err(DEV, "Digest integrity check FAILED: %llus +%u\n",
(unsigned long long)sector, data_size);
drbd_bcast_ee(mdev, "digest failed",
dgs, dig_in, dig_vv, e);
drbd_free_ee(mdev, e);