| Subject | Re: [PATCH 48/64] drbd: Use struct_group() to zero algs | From | Bart Van Assche <> | Date | Wed, 28 Jul 2021 14:45:55 -0700 |
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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)?
Thanks,
Bart.
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