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

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Message-ID: <20181113142317.379dbaf7@vmware.local.home>
Date:   Tue, 13 Nov 2018 14:23:17 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Qian Cai <cai@....us>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        linux-kernel@...r.kernel.org, Petr Mladek <pmladek@...e.com>,
        "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 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. 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. 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.

-- Steve


> %d%d%d%d%d%d%s%s%s%d%s%d%d%d%s%s%s%s%s%d%s%d%s%s%s%d%s%d%d%s%s%d%s%s%d%d%s%s%s%s
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> %s%d%s%s%s%
> [  833.044728] ------------[ cut here ]------------
> [  833.137184] precision 60612 too large
> >