linux-kernel - Re: [PATCH v6 14/23] vsprintf: add new `%pA` format specifier

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Message-ID: <202205070117.28F31079@keescook>
Date:   Sat, 7 May 2022 01:19:08 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Miguel Ojeda <ojeda@...nel.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Gary Guo <gary@...yguo.net>,
        Alex Gaynor <alex.gaynor@...il.com>,
        Wedson Almeida Filho <wedsonaf@...gle.com>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>
Subject: Re: [PATCH v6 14/23] vsprintf: add new `%pA` format specifier

On Sat, May 07, 2022 at 07:24:12AM +0200, Miguel Ojeda wrote:
> From: Gary Guo <gary@...yguo.net>
> 
> This patch adds a format specifier `%pA` to `vsprintf` which formats
> a pointer as `core::fmt::Arguments`. Doing so allows us to directly
> format to the internal buffer of `printf`, so we do not have to use
> a temporary buffer on the stack to pre-assemble the message on
> the Rust side.
> 
> This specifier is intended only to be used from Rust and not for C, so
> `checkpatch.pl` is intentionally unchanged to catch any misuse.

Maybe add a test to yell if pA is seen in a .c file (like the runtime
check in this patch).

But that can be separate from this patch.

Reviewed-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook