linux-hardening - Re: [RFC PATCH 1/1] vsprintf: Warn on integer scanning overflows

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Message-ID: <ZIIAnhriitHDR2Vq@smile.fi.intel.com>
Date:   Thu, 8 Jun 2023 19:23:58 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Richard Weinberger <richard@....at>
Cc:     linux-hardening <linux-hardening@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Kees Cook <keescook@...omium.org>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        senozhatsky <senozhatsky@...omium.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        davem <davem@...emloft.net>, edumazet <edumazet@...gle.com>,
        kuba <kuba@...nel.org>, pabeni <pabeni@...hat.com>,
        Miguel Ojeda <ojeda@...nel.org>,
        Alex Gaynor <alex.gaynor@...il.com>,
        Wedson Almeida Filho <wedsonaf@...il.com>,
        Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
        Björn Roy Baron <bjorn3_gh@...tonmail.com>,
        Benno Lossin <benno.lossin@...ton.me>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>
Subject: Re: [RFC PATCH 1/1] vsprintf: Warn on integer scanning overflows

On Thu, Jun 08, 2023 at 06:14:33PM +0200, Richard Weinberger wrote:
> ----- Ursprüngliche Mail -----
> > Von: "Andy Shevchenko" <andriy.shevchenko@...ux.intel.com>
> >>  	if (prefix_chars < max_chars) {
> >>  		rv = _parse_integer_limit(cp, base, &result, max_chars - prefix_chars);
> >> +		WARN_ON_ONCE(rv & KSTRTOX_OVERFLOW);
> > 
> > This seems incorrect. simple_strto*() are okay to overflow. It's by design.
> 
> Is this design decision also known to all users of scanf functions in the kernel?

We have test_scanf.c. Does it miss any test cases? Please add them!

-- 
With Best Regards,
Andy Shevchenko