[PATCH 48/64] drbd: Use struct_group() to zero algs

Kees Cook
2021-07-27T21:36:57Z

In preparation for FORTIFY_SOURCE performing compile-time and run-time
field bounds checking for memset(), avoid intentionally writing across
neighboring fields.

Add a struct_group() for the algs so that memset() can correctly reason
about the size.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
drivers/block/drbd/drbd_main.c | 3 ++-
drivers/block/drbd/drbd_protocol.h | 6 ++++--
drivers/block/drbd/drbd_receiver.c | 3 ++-
3 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 55234a558e98..b824679cfcb2 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -729,7 +729,8 @@ int drbd_send_sync_param(struct drbd_peer_device *peer_device)
cmd = apv >= 89 ? P_SYNC_PARAM89 : P_SYNC_PARAM;

/* initialize verify_alg and csums_alg */
- memset(p->verify_alg, 0, 2 * SHARED_SECRET_MAX);
+ BUILD_BUG_ON(sizeof(p->algs) != 2 * SHARED_SECRET_MAX);
+ memset(&p->algs, 0, sizeof(p->algs));

if (get_ldev(peer_device->device)) {
dc = rcu_dereference(peer_device->device->ldev->disk_conf);
diff --git a/drivers/block/drbd/drbd_protocol.h b/drivers/block/drbd/drbd_protocol.h
index dea59c92ecc1..a882b65ab5d2 100644
--- a/drivers/block/drbd/drbd_protocol.h
+++ b/drivers/block/drbd/drbd_protocol.h
@@ -283,8 +283,10 @@ struct p_rs_param_89 {

struct p_rs_param_95 {
u32 resync_rate;
- char verify_alg[SHARED_SECRET_MAX];
- char csums_alg[SHARED_SECRET_MAX];
+ struct_group(algs,
+ char verify_alg[SHARED_SECRET_MAX];
+ char csums_alg[SHARED_SECRET_MAX];
+ );
u32 c_plan_ahead;
u32 c_delay_target;
u32 c_fill_target;
diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index 1f740e42e457..6df2539e215b 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -3921,7 +3921,8 @@ static int receive_SyncParam(struct drbd_connection *connection, struct packet_i

/* initialize verify_alg and csums_alg */
p = pi->data;
- memset(p->verify_alg, 0, 2 * SHARED_SECRET_MAX);
+ BUILD_BUG_ON(sizeof(p->algs) != 2 * SHARED_SECRET_MAX);
+ memset(&p->algs, 0, sizeof(p->algs));

err = drbd_recv_all(peer_device->connection, p, header_size);
if (err)
--
2.30.2