linux-hardening - [PATCH][next] misc: bcm-vk: Replace zero-length array with flexible array member

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Date:   Fri, 14 May 2021 18:08:01 -0500
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     Scott Branden <scott.branden@...adcom.com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     bcm-kernel-feedback-list@...adcom.com,
        linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        linux-hardening@...r.kernel.org
Subject: [PATCH][next] misc: bcm-vk: Replace zero-length array with flexible
 array member

There is a regular need in the kernel to provide a way to declare
having a dynamically sized set of trailing elements in a structure.
Kernel code should always use “flexible array members”[1] for these
cases. The older style of one-element or zero-length arrays should
no longer be used[2].

Also, make use of the struct_size() helper in kzalloc().

[1] https://en.wikipedia.org/wiki/Flexible_array_member
[2] https://www.kernel.org/doc/html/v5.10/process/deprecated.html#zero-length-and-one-element-arrays

Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
---
 drivers/misc/bcm-vk/bcm_vk_msg.c | 3 +--
 drivers/misc/bcm-vk/bcm_vk_msg.h | 2 +-
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/misc/bcm-vk/bcm_vk_msg.c b/drivers/misc/bcm-vk/bcm_vk_msg.c
index f40cf08a6192..6efc52b49af6 100644
--- a/drivers/misc/bcm-vk/bcm_vk_msg.c
+++ b/drivers/misc/bcm-vk/bcm_vk_msg.c
@@ -701,8 +701,7 @@ int bcm_vk_send_shutdown_msg(struct bcm_vk *vk, u32 shut_type,
 		return -EINVAL;
 	}
 
-	entry = kzalloc(sizeof(*entry) +
-			sizeof(struct vk_msg_blk), GFP_KERNEL);
+	entry = kzalloc(struct_size(entry, to_v_msg, 1), GFP_KERNEL);
 	if (!entry)
 		return -ENOMEM;
 
diff --git a/drivers/misc/bcm-vk/bcm_vk_msg.h b/drivers/misc/bcm-vk/bcm_vk_msg.h
index 4eaad84825d6..56784c8896d8 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[0];
+	struct vk_msg_blk to_v_msg[];
 };
 
 /* queue stats counters */
-- 
2.27.0