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Date:   Sat, 18 Sep 2021 19:11:47 +0200
From:   Len Baker <len.baker@....com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Len Baker <len.baker@....com>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Christian K├Ânig <christian.koenig@....com>,
        Colin Ian King <colin.king@...onical.com>,
        linux-hardening@...r.kernel.org, linux-hyperv@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linaro-mm-sig@...ts.linaro.org
Subject: Re: [PATCH] net: mana: Prefer struct_size over open coded arithmetic

Hi Kees,

On Sat, Sep 18, 2021 at 06:51:51AM -0700, Kees Cook wrote:
>
>
> On September 18, 2021 6:20:10 AM PDT, Len Baker <len.baker@....com> wrote:
> >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@....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?.
>
> That is the "Media" subsystem patch tracker. The patch appears to be for networking, so the Media tracker has marked it as "not applicable [to the media subsystem]".
>
> The CC list for this patch seems rather wide (media, dri). I would have expected only netdev. Were you using scripts/get_maintainer.pl for getting addresses?

Yes, my workflow is scripts/checkpatch.pl and then scripts/get_maintainer.pl
before sending any patch :)

Regards,
Len
>
> -Kees

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