linux-kernel - Re: [PATCH] lz4: add overrun checks to lz4_uncompress

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Message-Id: <53D20E890200007800025C54@mail.emea.novell.com>
Date:	Fri, 25 Jul 2014 07:00:09 +0100
From:	"Jan Beulich" <JBeulich@...e.com>
To:	"Greg KH" <gregkh@...uxfoundation.org>,
	"Don A. Bailey" <donb@...uritymouse.com>
Cc:	<linux-kernel@...r.kernel.org>, <stable@...r.kernel.org>
Subject: Re: [PATCH] lz4: add overrun checks to
 lz4_uncompress_unknownoutputsize()

>>> On 04.07.14 at 15:01,  wrote:
>>>> On 04.07.14 at 08:12, Jan Beulich wrote:
> >>>> On 04.07.14 at 01:11, <gregkh@...uxfoundation.org> wrote:
> > > From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > > 
> > > Jan points out that I forgot to make the needed fixes to the
> > > lz4_uncompress_unknownoutputsize() function to mirror the changes done
> > > in lz4_decompress() with regards to potential pointer overflows.
> > 
> > Except that meanwhile Don agreed with my statement that neither
> > this nor the two earlier patches really fix the issue. So rather than
> > pushing this into 3.16 and stable trees, I wonder whether the two
> > earlier ones shouldn't be reverted and then a clean and correct
> > fix be applied.
> 
> So here's a patch which I think adds the missing pieces.

There wasn't any feedback at all so far, which I'm irritated by.
Did I do anything obviously wrong without noticing myself?

Jan

> lz4: check for underruns
> 
> While overruns are already being taken care of, underruns (resulting
> from overflows in the respective "op + length" (or similar) operations
> weren't. Fix this, allowing commits 4a3a990451, 4148c1f67a, and
> 206204a116 to be reverted (perhaps apart from the return value
> adjustments two of the three do).
> 
> Signed-off-by: Jan Beulich <jbeulich@...e.com>
> ---
> The patch applies correctly with or without said reverts carried out.
> 
> --- a/lib/lz4/lz4_decompress.c
> +++ b/lib/lz4/lz4_decompress.c
> @@ -89,6 +89,8 @@ static int lz4_uncompress(const char *so
>  			ip += length;
>  			break; /* EOF */
>  		}
> +		if (unlikely((unsigned long)cpy < (unsigned long)op))
> +			goto _output_error;
>  		LZ4_WILDCOPY(ip, op, cpy);
>  		ip -= (op - cpy);
>  		op = cpy;
> @@ -147,6 +149,8 @@ static int lz4_uncompress(const char *so
>  				goto _output_error;
>  			continue;
>  		}
> +		if (unlikely((unsigned long)cpy < (unsigned long)op))
> +			goto _output_error;
>  		LZ4_SECURECOPY(ref, op, cpy);
>  		op = cpy; /* correction */
>  	}
> @@ -209,6 +213,8 @@ static int lz4_uncompress_unknownoutputs
>  			op += length;
>  			break;/* Necessarily EOF, due to parsing restrictions */
>  		}
> +		if (unlikely((unsigned long)cpy < (unsigned long)op))
> +			goto _output_error;
>  		LZ4_WILDCOPY(ip, op, cpy);
>  		ip -= (op - cpy);
>  		op = cpy;
> @@ -272,6 +278,8 @@ static int lz4_uncompress_unknownoutputs
>  				goto _output_error;
>  			continue;
>  		}
> +		if (unlikely((unsigned long)cpy < (unsigned long)op))
> +			goto _output_error;
>  		LZ4_SECURECOPY(ref, op, cpy);
>  		op = cpy; /* correction */
>  	}
> 
> 
> 



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