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SubjectRe: [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@linuxfoundation.org> wrote:
> > > From: Greg Kroah-Hartman <gregkh@linuxfoundation.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@suse.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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