[patch 32/38] XZ decompressor: Fix decoding of empty LZMA2 streams

[Greg KH]

2.6.38-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Lasse Collin <lasse.collin@xxxxxxxxxxx>

commit 646032e3b05b32d3f20cb108a030593d9d792eb5 upstream.

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 <lasse.collin@xxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

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

--- a/lib/xz/xz_dec_lzma2.c
+++ b/lib/xz/xz_dec_lzma2.c
@@ -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;
 


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