linux-kernel - Re: WARNING: CPU: 26 PID: 64391 at lib/vsprintf.c:2193 set

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Message-ID: <20181114093819.GL10650@smile.fi.intel.com>
Date:   Wed, 14 Nov 2018 11:38:19 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Petr Mladek <pmladek@...e.com>
Cc:     Steven Rostedt <rostedt@...dmis.org>, Qian Cai <cai@....us>,
        linux-kernel@...r.kernel.org, "Tobin C. Harding" <me@...in.cc>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Rasmus Villemoes <rasmus.villemoes@...vas.dk>
Subject: Re: WARNING: CPU: 26 PID: 64391 at lib/vsprintf.c:2193
 set_precision+0x84/0x90

On Wed, Nov 14, 2018 at 12:05:12AM +0100, Petr Mladek wrote:
> On Tue 2018-11-13 14:23:17, Steven Rostedt wrote:
> > On Tue, 13 Nov 2018 13:58:18 -0500
> > Qian Cai <cai@....us> wrote:
> > 
> > > > Care to print the len and name parameters before this line?  
> > > len = 60612; name =
> > 
> > How big are pages on arm64? Because we shouldn't get to this path if
> > the string is bigger than PAGE_SIZE. But I know that on PPC64,
> > PAGE_SIZE can be 64K, and 60612 is less than that. Thus, if we get
> > there, the test is against signed int:16 (16 bit signed integer) that
> > can go up to most 32768. If the string size is bigger than that, you
> > would get this error.
> > 
> > I would just say to ignore it.
> 
> I tend to agree.
> 
> > The only thing that can happen if
> > someone does this is to trigger the warning. Unless if it is considered
> > a form of DOS, where userspace just bombards the console by triggering
> > this waring.
> 
> We are actually on the safe side because it is WARN_ONCE().
> 
> > But I don't see a problem with the actual design. There's
> > no reason we should be processing string variables bigger than 32768 in
> > vsprintf.
> 
> It is not even needed in this case. The string is limited also by
> MODULE_NAME_LEN.

At least not in this code.

Are you proposing to replace strlen(name) with strnlen(name, MODULE_NAME_LEN)?


-- 
With Best Regards,
Andy Shevchenko