2011-05-01 16:48:42

by Lasse Collin

Subject: [PATCH] XZ decompressor: Fix decoding of empty LZMA2 streams

From: Lasse Collin <[email protected]>

The old code considered valid empty LZMA2 streams to be corrupt.
Note that a typical empty .xz file has no LZMA2 data at all,
and thus most .xz files having no uncompressed data are handled
correctly even without this fix.

Signed-off-by: Lasse Collin <[email protected]>
---

lib/xz/xz_dec_lzma2.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff -uprN linux-2.6.39-rc5-git5.orig/lib/xz/xz_dec_lzma2.c linux-2.6.39-rc5-git5/lib/xz/xz_dec_lzma2.c
--- linux-2.6.39-rc5-git5.orig/lib/xz/xz_dec_lzma2.c 2011-05-01 17:56:38.000000000 +0300
+++ linux-2.6.39-rc5-git5/lib/xz/xz_dec_lzma2.c 2011-05-01 18:06:03.000000000 +0300
@@ -969,6 +969,9 @@ XZ_EXTERN enum xz_ret xz_dec_lzma2_run(s
*/
tmp = b->in[b->in_pos++];

+ if (tmp == 0x00)
+ return XZ_STREAM_END;
+
if (tmp >= 0xE0 || tmp == 0x01) {
s->lzma2.need_props = true;
s->lzma2.need_dict_reset = false;
@@ -1001,9 +1004,6 @@ XZ_EXTERN enum xz_ret xz_dec_lzma2_run(s
lzma_reset(s);
}
} else {
- if (tmp == 0x00)
- return XZ_STREAM_END;
-
if (tmp > 0x02)
return XZ_DATA_ERROR;

2011-05-03 21:36:43

by Andrew Morton

Subject: Re: [PATCH] XZ decompressor: Fix decoding of empty LZMA2 streams

On Sun, 1 May 2011 19:38:42 +0300
Lasse Collin <[email protected]> wrote:

> From: Lasse Collin <[email protected]>
>
> The old code considered valid empty LZMA2 streams to be corrupt.
> Note that a typical empty .xz file has no LZMA2 data at all,
> and thus most .xz files having no uncompressed data are handled
> correctly even without this fix.
>
> Signed-off-by: Lasse Collin <[email protected]>

The patch didn't have the cc:stable tag, but appears to be needed in
2.6.38.x and perhaps earlier, yes?

It's commit 646032e3b05b32d3f20cb108a030593d9d792eb5 in mainline.

>
> lib/xz/xz_dec_lzma2.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff -uprN linux-2.6.39-rc5-git5.orig/lib/xz/xz_dec_lzma2.c linux-2.6.39-rc5-git5/lib/xz/xz_dec_lzma2.c
> --- linux-2.6.39-rc5-git5.orig/lib/xz/xz_dec_lzma2.c 2011-05-01 17:56:38.000000000 +0300
> +++ linux-2.6.39-rc5-git5/lib/xz/xz_dec_lzma2.c 2011-05-01 18:06:03.000000000 +0300
> @@ -969,6 +969,9 @@ XZ_EXTERN enum xz_ret xz_dec_lzma2_run(s
> */
> tmp = b->in[b->in_pos++];
>
> + if (tmp == 0x00)
> + return XZ_STREAM_END;
> +
> if (tmp >= 0xE0 || tmp == 0x01) {
> s->lzma2.need_props = true;
> s->lzma2.need_dict_reset = false;
> @@ -1001,9 +1004,6 @@ XZ_EXTERN enum xz_ret xz_dec_lzma2_run(s
> lzma_reset(s);
> }
> } else {
> - if (tmp == 0x00)
> - return XZ_STREAM_END;
> -
> if (tmp > 0x02)
> return XZ_DATA_ERROR;
>

2011-05-03 22:22:29

by Lasse Collin

Subject: Re: [PATCH] XZ decompressor: Fix decoding of empty LZMA2 streams

On 2011-05-04 Andrew Morton wrote:
> Lasse Collin <[email protected]> wrote:
> > From: Lasse Collin <[email protected]>
> >
> > The old code considered valid empty LZMA2 streams to be corrupt.
> > Note that a typical empty .xz file has no LZMA2 data at all,
> > and thus most .xz files having no uncompressed data are handled
> > correctly even without this fix.
> >
> > Signed-off-by: Lasse Collin <[email protected]>
>
> The patch didn't have the cc:stable tag, but appears to be needed in
> 2.6.38.x and perhaps earlier, yes?
>
> It's commit 646032e3b05b32d3f20cb108a030593d9d792eb5 in mainline.

Thanks. It's good for 2.6.38.x. Older ones don't have XZ support.

--
Lasse Collin | IRC: Larhzu @ IRCnet & Freenode

2011-05-04 23:18:49

by Greg KH

Subject: Re: [stable] [PATCH] XZ decompressor: Fix decoding of empty LZMA2 streams

On Wed, May 04, 2011 at 01:22:36AM +0300, Lasse Collin wrote:
> On 2011-05-04 Andrew Morton wrote:
> > Lasse Collin <[email protected]> wrote:
> > > From: Lasse Collin <[email protected]>
> > >
> > > The old code considered valid empty LZMA2 streams to be corrupt.
> > > Note that a typical empty .xz file has no LZMA2 data at all,
> > > and thus most .xz files having no uncompressed data are handled
> > > correctly even without this fix.
> > >
> > > Signed-off-by: Lasse Collin <[email protected]>
> >
> > The patch didn't have the cc:stable tag, but appears to be needed in
> > 2.6.38.x and perhaps earlier, yes?
> >
> > It's commit 646032e3b05b32d3f20cb108a030593d9d792eb5 in mainline.
>
> Thanks. It's good for 2.6.38.x. Older ones don't have XZ support.

Now queued up, thanks.

greg k-h