unlzma: fix too-eager corruption check

function                                             old     new   delta
unpack_lzma_stream                                  2686    2674     -12

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 13 insertions, 7 deletions

diff --git a/archival/libarchive/decompress_unlzma.c b/archival/libarchive/decompress_unlzma.c
index 6886239d0..668b01618 100644
--- a/archival/libarchive/decompress_unlzma.c
+++ b/archival/libarchive/decompress_unlzma.c
@@ -353,8 +353,10 @@ unpack_lzma_stream(transformer_state_t *xstate)
                                                 if ((int32_t)pos < 0) {
                                                         pos += header.dict_size;
                                                         /* see unzip_bad_lzma_2.zip: */
-                                                        if (pos >= buffer_size)
+                                                        if (pos >= buffer_size) {
+                                                                dbg("%d pos:%d buffer_size:%d", __LINE__, pos, buffer_size);
                                                                 goto bad;
+                                                        }
                                                 }
                                                 previous_byte = buffer[pos];
                                                 goto one_byte1;
@@ -430,10 +432,9 @@ unpack_lzma_stream(transformer_state_t *xstate)
                                                 for (; num_bits2 != LZMA_NUM_ALIGN_BITS; num_bits2--)
                                                         rep0 = (rep0 << 1) | rc_direct_bit(rc);
                                                 rep0 <<= LZMA_NUM_ALIGN_BITS;
-                                                if ((int32_t)rep0 < 0) {
-                                                        dbg("%d rep0:%d", __LINE__, rep0);
-                                                        goto bad;
-                                                }
+                                                // Note: (int32_t)rep0 may be < 0 here
+                                                // (I have linux-3.3.4.tar.lzma which has it).
+                                                // I moved the check after "++rep0 == 0" check below.
                                                 prob3 = p + LZMA_ALIGN;
                                         }
                                         i2 = 1;
@@ -444,8 +445,13 @@ unpack_lzma_stream(transformer_state_t *xstate)
                                                 i2 <<= 1;
                                         }
                                 }
-                                if (++rep0 == 0)
-                                        break;
+                                rep0++;
+                                if ((int32_t)rep0 <= 0) {
+                                        if (rep0 == 0)
+                                                break;
+                                        dbg("%d rep0:%d", __LINE__, rep0);
+                                        goto bad;
+                                }
                         }
 
                         len += LZMA_MATCH_MIN_LEN;