XZ decompressor: Fix decoding of empty LZMA2 streams

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@tukaani.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 3 deletions

diff --git a/lib/xz/xz_dec_lzma2.c b/lib/xz/xz_dec_lzma2.c
index ea5fa4fe9d67..a6cdc969ea42 100644
--- 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(struct xz_dec_lzma2 *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(struct xz_dec_lzma2 *s,
                                                 lzma_reset(s);
                                 }
                         } else {
-                                if (tmp == 0x00)
-                                        return XZ_STREAM_END;
-
                                 if (tmp > 0x02)
                                         return XZ_DATA_ERROR;