[PATCH] misc: bcm-vk: Annotate struct bcm_vk_wkent with __counted_by

[PATCH] misc: bcm-vk: Annotate struct bcm_vk_wkent with __counted_by

[Kees Cook]

Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
(for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).

As found with Coccinelle[1], add __counted_by for struct bcm_vk_wkent.
Additionally, since the element count member must be set before accessing
the annotated flexible array member, move its initialization earlier.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci

Cc: Scott Branden <scott.branden@broadcom.com>
Cc: Broadcom internal kernel review list <bcm-kernel-feedback-list@broadcom.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 drivers/misc/bcm-vk/bcm_vk_msg.c | 2 +-
 drivers/misc/bcm-vk/bcm_vk_msg.h | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/misc/bcm-vk/bcm_vk_msg.c b/drivers/misc/bcm-vk/bcm_vk_msg.c
index e17d81231ea6..1f42d1d5a630 100644
--- a/drivers/misc/bcm-vk/bcm_vk_msg.c
+++ b/drivers/misc/bcm-vk/bcm_vk_msg.c
@@ -703,12 +703,12 @@ int bcm_vk_send_shutdown_msg(struct bcm_vk *vk, u32 shut_type,
 	entry = kzalloc(struct_size(entry, to_v_msg, 1), GFP_KERNEL);
 	if (!entry)
 		return -ENOMEM;
+	entry->to_v_blks = 1;	/* always 1 block */
 
 	/* fill up necessary data */
 	entry->to_v_msg[0].function_id = VK_FID_SHUTDOWN;
 	set_q_num(&entry->to_v_msg[0], q_num);
 	set_msg_id(&entry->to_v_msg[0], VK_SIMPLEX_MSG_ID);
-	entry->to_v_blks = 1; /* always 1 block */
 
 	entry->to_v_msg[0].cmd = shut_type;
 	entry->to_v_msg[0].arg = pid;
diff --git a/drivers/misc/bcm-vk/bcm_vk_msg.h b/drivers/misc/bcm-vk/bcm_vk_msg.h
index 56784c8896d8..157495e48f15 100644
--- a/drivers/misc/bcm-vk/bcm_vk_msg.h
+++ b/drivers/misc/bcm-vk/bcm_vk_msg.h
@@ -116,7 +116,7 @@ struct bcm_vk_wkent {
 	u32 usr_msg_id;
 	u32 to_v_blks;
 	u32 seq_num;
-	struct vk_msg_blk to_v_msg[];
+	struct vk_msg_blk to_v_msg[] __counted_by(to_v_blks);
 };
 
 /* queue stats counters */
-- 
2.34.1

Re: [PATCH] misc: bcm-vk: Annotate struct bcm_vk_wkent with __counted_by

[Gustavo A. R. Silva]

On 9/22/23 11:50, Kees Cook wrote:
> Prepare for the coming implementation by GCC and Clang of the __counted_by
> attribute. Flexible array members annotated with __counted_by can have
> their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
> (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> functions).
> 
> As found with Coccinelle[1], add __counted_by for struct bcm_vk_wkent.
> Additionally, since the element count member must be set before accessing
> the annotated flexible array member, move its initialization earlier.
> 
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
> 
> Cc: Scott Branden <scott.branden@broadcom.com>
> Cc: Broadcom internal kernel review list <bcm-kernel-feedback-list@broadcom.com>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Signed-off-by: Kees Cook <keescook@chromium.org>

Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Thanks
-- 
Gustavo

> ---
>   drivers/misc/bcm-vk/bcm_vk_msg.c | 2 +-
>   drivers/misc/bcm-vk/bcm_vk_msg.h | 2 +-
>   2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/misc/bcm-vk/bcm_vk_msg.c b/drivers/misc/bcm-vk/bcm_vk_msg.c
> index e17d81231ea6..1f42d1d5a630 100644
> --- a/drivers/misc/bcm-vk/bcm_vk_msg.c
> +++ b/drivers/misc/bcm-vk/bcm_vk_msg.c
> @@ -703,12 +703,12 @@ int bcm_vk_send_shutdown_msg(struct bcm_vk *vk, u32 shut_type,
>   	entry = kzalloc(struct_size(entry, to_v_msg, 1), GFP_KERNEL);
>   	if (!entry)
>   		return -ENOMEM;
> +	entry->to_v_blks = 1;	/* always 1 block */
>   
>   	/* fill up necessary data */
>   	entry->to_v_msg[0].function_id = VK_FID_SHUTDOWN;
>   	set_q_num(&entry->to_v_msg[0], q_num);
>   	set_msg_id(&entry->to_v_msg[0], VK_SIMPLEX_MSG_ID);
> -	entry->to_v_blks = 1; /* always 1 block */
>   
>   	entry->to_v_msg[0].cmd = shut_type;
>   	entry->to_v_msg[0].arg = pid;
> diff --git a/drivers/misc/bcm-vk/bcm_vk_msg.h b/drivers/misc/bcm-vk/bcm_vk_msg.h
> index 56784c8896d8..157495e48f15 100644
> --- a/drivers/misc/bcm-vk/bcm_vk_msg.h
> +++ b/drivers/misc/bcm-vk/bcm_vk_msg.h
> @@ -116,7 +116,7 @@ struct bcm_vk_wkent {
>   	u32 usr_msg_id;
>   	u32 to_v_blks;
>   	u32 seq_num;
> -	struct vk_msg_blk to_v_msg[];
> +	struct vk_msg_blk to_v_msg[] __counted_by(to_v_blks);
>   };
>   
>   /* queue stats counters */