linux-kernel - Re: [PATCH] audit: Use struct_size() helper in alloc

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Date:   Mon, 1 Jun 2020 11:36:09 -0400
From:   Paul Moore <paul@...l-moore.com>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc:     Eric Paris <eparis@...hat.com>, linux-audit@...hat.com,
        linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH] audit: Use struct_size() helper in alloc_chunk

On Sun, May 24, 2020 at 4:47 PM Gustavo A. R. Silva
<gustavoars@...nel.org> wrote:
> One of the more common cases of allocation size calculations is finding
> the size of a structure that has a zero-sized array at the end, along
> with memory for some number of elements for that array. For example:
>
> struct audit_chunk {
>         ...
>         struct node {
>                 struct list_head list;
>                 struct audit_tree *owner;
>                 unsigned index;         /* index; upper bit indicates 'will prune' */
>         } owners[];
> };
>
> Make use of the struct_size() helper instead of an open-coded version
> in order to avoid any potential type mistakes.
>
> So, replace the following form:
>
> offsetof(struct audit_chunk, owners) + count * sizeof(struct node);
>
> with:
>
> struct_size(chunk, owners, count)
>
> This code was detected with the help of Coccinelle.
>
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
> ---
>  kernel/audit_tree.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)

Thanks, this looks reasonable to me, but it came in too late for the
v5.8 merge window (I dislike taking changes past -rc5/6 unless
critical).  Once the merge window closes I'll merge this into
audit/next.

-- 
paul moore
www.paul-moore.com