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>
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 6afb81f..451fc36 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -2537,10 +2537,36 @@
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);
diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index d0e19a2..ca213c6 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -1281,7 +1281,8 @@
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);