linux-kernel - Re: [PATCH] vsprintf: protect kernel from panic due to non-canonical pointer dereference

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Message-ID: <Y0/ep9LS5jVTrUWI@smile.fi.intel.com>
Date:   Wed, 19 Oct 2022 14:25:27 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Haakon Bugge <haakon.bugge@...cle.com>
Cc:     Jane Chu <jane.chu@...cle.com>, Petr Mladek <pmladek@...e.com>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        "senozhatsky@...omium.org" <senozhatsky@...omium.org>,
        "linux@...musvillemoes.dk" <linux@...musvillemoes.dk>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        John Haxby <john.haxby@...cle.com>
Subject: Re: [PATCH] vsprintf: protect kernel from panic due to non-canonical
 pointer dereference

On Wed, Oct 19, 2022 at 10:43:07AM +0000, Haakon Bugge wrote:
> > On 18 Oct 2022, at 22:49, Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:
> > On Tue, Oct 18, 2022 at 08:30:01PM +0000, Jane Chu wrote:

...

> > Obviously, to see the crash. And let kernel _to crash_. Isn't it what we need
> > to see a bug as early as possible?
> 
> If you follow that argument, why doesn't the kernel crash when the pointer
> is, e.g., a NULL pointer? According to you, shouldn't it crash a early as
> possible in that case also?

Because it is _special_. It's not just an invalid pointer. There may be
very well good cases where we supply (valid!) NULL pointers to the printf().

-- 
With Best Regards,
Andy Shevchenko