On Wed, Jul 28, 2021 at 02:45:55PM -0700, Bart Van Assche wrote:
On 7/27/21 1:58 PM, Kees Cook wrote:
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));
Using struct_group() introduces complexity. Has it been considered not to modify struct p_rs_param_95 and instead to use two memset() calls instead of one (one memset() call per member)?
I went this direction because using two memset()s (or memcpy()s in other patches) changes the machine code. It's not much of a change, but it seems easier to justify "no binary changes" via the use of struct_group().
If splitting the memset() is preferred, I can totally do that instead. :)
-Kees