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Commit 470be44a authored by Lars Ellenberg's avatar Lars Ellenberg Committed by Philipp Reisner
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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: default avatarPhilipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: default avatarLars Ellenberg <lars.ellenberg@linbit.com>
parent 5f9915bb

drivers/block/drbd/drbd_main.c

+27 −1
Original line number Diff line number Diff line
@@ -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);

drivers/block/drbd/drbd_receiver.c

+2 −1
Original line number Diff line number Diff line
@@ -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);