From: Kees Cook <kees@kernel.org>
To: Bill Wendling <morbo@google.com>
Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>,
linux-hardening@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] overflow: Match arithmetic in both parts of __builtin_choose_expr
Date: Mon, 12 Oct 2026 20:30:10 -0700 [thread overview]
Message-ID: <202610122028.BB0EDC98@keescook> (raw)
In-Reply-To: <20261012205919.4012405-1-morbo@google.com>
On Mon, Oct 12, 2026 at 08:59:19PM +0000, Bill Wendling wrote:
> The two parts of the '__builtin_choose_expr()' had different arithmetic
> expressions. This patch correct it so that both parts calculate:
>
> COUNT * sizeof(*MEMBER) + __must_be_array(MEMBER)
>
> In practice, the call to '__must_be_array' is meant to assert if
> 'MEMBER' isn't an array and return '0' otherwise. However, symmetry is
> less prone to subtle errors (and far more satisfying).
>
> Fixes: 230f6fa2c1db ("overflow: Provide constant expression struct_size")
A Fixes trailer implies a bug being solved. What problem is there here?
I only see downsides to this change: this adds even more layers of
macros and inlinings to gain the size_add() for a constant integer 0.
?
> - size_mul(count, sizeof(*(p)->member) + __must_be_array((p)->member)))
> + size_add(size_mul(count, sizeof(*(p)->member)), \
> + __must_be_array((p)->member)))
--
Kees Cook
next prev parent reply other threads:[~2026-10-13 3:30 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-12 20:59 [PATCH] overflow: Match arithmetic in both parts of __builtin_choose_expr Bill Wendling
2026-10-13 3:30 ` Kees Cook [this message]
2026-10-13 17:17 ` Bill Wendling
2026-10-13 20:31 ` [PATCH v2] " Bill Wendling
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=202610122028.BB0EDC98@keescook \
--to=kees@kernel.org \
--cc=gustavoars@kernel.org \
--cc=linux-hardening@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=morbo@google.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.