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

Message ID 20210727205855.411487-49-keescook@chromium.org
State New
Headers show
Series
  • Introduce strict memcpy() bounds checking
Related show

Commit Message

Kees Cook July 27, 2021, 8:58 p.m.
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(-)

Comments

Bart Van Assche July 28, 2021, 9:45 p.m. | #1
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.
Bart Van Assche July 30, 2021, 2:57 a.m. | #2
On 7/29/21 7:31 PM, Kees Cook wrote:
> 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.

> :)


I don't have a strong opinion about this. Lars, do you want to comment
on this patch?

Thanks,

Bart.
Lars Ellenberg July 30, 2021, 9:25 a.m. | #3
On Thu, Jul 29, 2021 at 07:57:47PM -0700, Bart Van Assche wrote:
> On 7/29/21 7:31 PM, Kees Cook wrote:
> > 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.
> > :)
> 
> I don't have a strong opinion about this. Lars, do you want to comment
> on this patch?


Fine either way. "no binary changes" sounds good ;-)

Thanks,
    Lars

Patch

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)