linux-kernel - Re: [PATCH] lib/string_helpers.c: fix infinite loop in string_get

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Date:	Mon, 14 Sep 2015 12:06:35 +0300
From:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:	James Bottomley <jbottomley@...n.com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
Cc:	"linux@...musvillemoes.dk" <linux@...musvillemoes.dk>,
	"vkuznets@...hat.com" <vkuznets@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kys@...rosoft.com" <kys@...rosoft.com>
Subject: Re: [PATCH] lib/string_helpers.c: fix infinite loop in
 string_get_size()

On Fri, 2015-09-11 at 18:31 +0000, James Bottomley wrote:
> On Thu, 2015-09-10 at 16:08 -0700, Andrew Morton wrote:
> > On Fri,  4 Sep 2015 14:56:33 +0200 Vitaly Kuznetsov <
> > vkuznets@...hat.com> wrote:
> > 
> > > string_get_size(1, 512, 0, ..., ...) call results in an infinite 
> > > loop. The
> > > problem is that if size == 0 when we start calculating sf_cap 
> > > this loop
> > > will never end.
> > > 
> > > The caller causing the issue is sd_read_capacity(), the problem 
> > > was noticed
> > > on Hyper-V.
> > 
> > When fixing bugs, please provide enough info for others to be able 
> > to
> > understand which kernel version(s) need the fix.  In this case: 
> > what
> > end-user action triggers this bug?  (iow, how does sdkp->capacity
> > become zero?)
> 
> Any more details.  The attached programme, which is cut straight out 
> of
> the algorithm in string_helpers.c and modified for a C environment
> slightly (only in do_div and the typedefs) produces this
> 
> hello
> STRING IS 512 B
> 
> With your input, so I don't think the problem is where you think it 
> is.
> 
> James
> 

Vitaly, it might make sense to extend test-string_helpers.c to what you
are trying to do right.


-- 
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Intel Finland Oy
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