Re: [PATCH] net: mana: Prefer struct_size over open coded arithmetic

From: Len Baker <len.baker@gmx.com>
To: "K. Y. Srinivasan" <kys@microsoft.com>,
	"Haiyang Zhang" <haiyangz@microsoft.com>,
	"Stephen Hemminger" <sthemmin@microsoft.com>,
	"Wei Liu" <wei.liu@kernel.org>,
	"Dexuan Cui" <decui@microsoft.com>,
	"David S. Miller" <davem@davemloft.net>,
	"Jakub Kicinski" <kuba@kernel.org>,
	"Sumit Semwal" <sumit.semwal@linaro.org>,
	"Christian König" <christian.koenig@amd.com>,
	"Kees Cook" <keescook@chromium.org>
Cc: Len Baker <len.baker@gmx.com>,
	Colin Ian King <colin.king@canonical.com>,
	linux-hardening@vger.kernel.org, linux-hyperv@vger.kernel.org,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org,
	linaro-mm-sig@lists.linaro.org
Subject: Re: [PATCH] net: mana: Prefer struct_size over open coded arithmetic
Date: Sat, 18 Sep 2021 15:20:10 +0200	[thread overview]
Message-ID: <20210918132010.GA15999@titan> (raw)
In-Reply-To: <20210911102818.3804-1-len.baker@gmx.com>

Hi,

On Sat, Sep 11, 2021 at 12:28:18PM +0200, Len Baker wrote:
> As noted in the "Deprecated Interfaces, Language Features, Attributes,
> and Conventions" documentation [1], size calculations (especially
> multiplication) should not be performed in memory allocator (or similar)
> function arguments due to the risk of them overflowing. This could lead
> to values wrapping around and a smaller allocation being made than the
> caller was expecting. Using those allocations could lead to linear
> overflows of heap memory and other misbehaviors.
>
> So, use the struct_size() helper to do the arithmetic instead of the
> argument "size + count * size" in the kzalloc() function.
>
> [1] https://www.kernel.org/doc/html/v5.14/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments
>
> Signed-off-by: Len Baker <len.baker@gmx.com>
> ---
>  drivers/net/ethernet/microsoft/mana/hw_channel.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/drivers/net/ethernet/microsoft/mana/hw_channel.c b/drivers/net/ethernet/microsoft/mana/hw_channel.c
> index 1a923fd99990..0efdc6c3c32a 100644
> --- a/drivers/net/ethernet/microsoft/mana/hw_channel.c
> +++ b/drivers/net/ethernet/microsoft/mana/hw_channel.c
> @@ -398,9 +398,7 @@ static int mana_hwc_alloc_dma_buf(struct hw_channel_context *hwc, u16 q_depth,
>  	int err;
>  	u16 i;
>
> -	dma_buf = kzalloc(sizeof(*dma_buf) +
> -			  q_depth * sizeof(struct hwc_work_request),
> -			  GFP_KERNEL);
> +	dma_buf = kzalloc(struct_size(dma_buf, reqs, q_depth), GFP_KERNEL);
>  	if (!dma_buf)
>  		return -ENOMEM;
>
> --
> 2.25.1
>

I have received a email from the linux-media subsystem telling that this
patch is not applicable. The email is the following:

Hello,

The following patch (submitted by you) has been updated in Patchwork:

 * linux-media: net: mana: Prefer struct_size over open coded arithmetic
     - http://patchwork.linuxtv.org/project/linux-media/patch/20210911102818.3804-1-len.baker@gmx.com/
     - for: Linux Media kernel patches
    was: New
    now: Not Applicable

This email is a notification only - you do not need to respond.

The question is: Why it is not applicable?. I have no received any bad comment
and a "Reviewed-by:" tag from Haiyang Zhang. So, what is the reason for the
"Not Applicable" state?.

Regards,
Len