[PATCH][next] bnx2x: Replace one-element array with flexible-array member

[PATCH][next] bnx2x: Replace one-element array with flexible-array member

[Gustavo A. R. Silva]

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].

This helps with the ongoing efforts to globally enable -Warray-bounds
and get us closer to being able to tighten the FORTIFY_SOURCE routines
on memcpy().

This issue was found with the help of Coccinelle and audited and fixed,
manually.

[1] https://en.wikipedia.org/wiki/Flexible_array_member
[2] https://www.kernel.org/doc/html/v5.16/process/deprecated.html#zero-length-and-one-element-arrays

Link: https://github.com/KSPP/linux/issues/79
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
 drivers/net/ethernet/broadcom/bnx2x/bnx2x.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/broadcom/bnx2x/bnx2x.h b/drivers/net/ethernet/broadcom/bnx2x/bnx2x.h
index a19dd6797070..447a75ea0cc1 100644
--- a/drivers/net/ethernet/broadcom/bnx2x/bnx2x.h
+++ b/drivers/net/ethernet/broadcom/bnx2x/bnx2x.h
@@ -1271,7 +1271,7 @@ struct bnx2x_fw_stats_data {
 	struct per_port_stats		port;
 	struct per_pf_stats		pf;
 	struct fcoe_statistics_params	fcoe;
-	struct per_queue_stats		queue_stats[1];
+	struct per_queue_stats		queue_stats[];
 };
 
 /* Public slow path states */
-- 
2.27.0

Re: [PATCH][next] bnx2x: Replace one-element array with flexible-array member

[Jakub Kicinski]

On Fri, 4 Feb 2022 17:21:44 -0600 Gustavo A. R. Silva wrote:
> 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].
> 
> This helps with the ongoing efforts to globally enable -Warray-bounds
> and get us closer to being able to tighten the FORTIFY_SOURCE routines
> on memcpy().
> 
> This issue was found with the help of Coccinelle and audited and fixed,
> manually.
> 
> [1] https://en.wikipedia.org/wiki/Flexible_array_member
> [2] https://www.kernel.org/doc/html/v5.16/process/deprecated.html#zero-length-and-one-element-arrays
> 
> Link: https://github.com/KSPP/linux/issues/79
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Would be useful to include the analysis confirming the change is safe
in this case, beyond the boiler plate commit message.

Reviewed-by: Jakub Kicinski <kuba@kernel.org>