misc: bcm-vk: Annotate struct bcm_vk_wkent with __counted_by

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 <[email protected]>

Cc Broadcom internal kernel review list <[email protected]>

Cc Arnd Bergmann <[email protected]>

Cc Greg Kroah-Hartman <[email protected]>

Signed-off-by Kees Cook <[email protected]>

---
  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(-)

drivers/misc/bcm-vk/bcm_vk_msg.c +1 -1

index e17d81231ea6..1f42d1d5a630 100644
@@ -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;

drivers/misc/bcm-vk/bcm_vk_msg.h +1 -1

index 56784c8896d8..157495e48f15 100644
@@ -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 */