bunzip2: fix runCnt overflow from bug 10431

This particular corrupted file can be dealth with by using "unsigned".
If there will be cases where it genuinely overflows, there is a disabled
code to deal with that too.

function                                             old     new   delta
get_next_block                                      1678    1667     -11

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

1 files changed, 19 insertions, 11 deletions

diff --git a/archival/libarchive/decompress_bunzip2.c b/archival/libarchive/decompress_bunzip2.c
index 7cd18f5ed..bec89edd3 100644
--- a/archival/libarchive/decompress_bunzip2.c
+++ b/archival/libarchive/decompress_bunzip2.c
@@ -156,15 +156,15 @@ static unsigned get_bits(bunzip_data *bd, int bits_wanted)
 static int get_next_block(bunzip_data *bd)
 {
         struct group_data *hufGroup;
-        int dbufCount, dbufSize, groupCount, *base, *limit, selector,
-                i, j, runPos, symCount, symTotal, nSelectors, byteCount[256];
-        int runCnt = runCnt; /* for compiler */
+        int groupCount, *base, *limit, selector,
+                i, j, symCount, symTotal, nSelectors, byteCount[256];
         uint8_t uc, symToByte[256], mtfSymbol[256], *selectors;
         uint32_t *dbuf;
         unsigned origPtr, t;
+        unsigned dbufCount, runPos;
+        unsigned runCnt = runCnt; /* for compiler */
 
         dbuf = bd->dbuf;
-        dbufSize = bd->dbufSize;
         selectors = bd->selectors;
 
 /* In bbox, we are ok with aborting through setjmp which is set up in start_bunzip */
@@ -187,7 +187,7 @@ static int get_next_block(bunzip_data *bd)
            it didn't actually work. */
         if (get_bits(bd, 1)) return RETVAL_OBSOLETE_INPUT;
         origPtr = get_bits(bd, 24);
-        if ((int)origPtr > dbufSize) return RETVAL_DATA_ERROR;
+        if (origPtr > bd->dbufSize) return RETVAL_DATA_ERROR;
 
         /* mapping table: if some byte values are never used (encoding things
            like ascii text), the compression code removes the gaps to have fewer
@@ -435,7 +435,14 @@ static int get_next_block(bunzip_data *bd)
                            symbols, but a run of length 0 doesn't mean anything in this
                            context).  Thus space is saved. */
                         runCnt += (runPos << nextSym); /* +runPos if RUNA; +2*runPos if RUNB */
-                        if (runPos < dbufSize) runPos <<= 1;
+//The 32-bit overflow of runCnt wasn't yet seen, but probably can happen.
+//This would be the fix (catches too large count way before it can overflow):
+//                      if (runCnt > bd->dbufSize) {
+//                              dbg("runCnt:%u > dbufSize:%u RETVAL_DATA_ERROR",
+//                                              runCnt, bd->dbufSize);
+//                              return RETVAL_DATA_ERROR;
+//                      }
+                        if (runPos < bd->dbufSize) runPos <<= 1;
                         goto end_of_huffman_loop;
                 }
 
@@ -445,14 +452,15 @@ static int get_next_block(bunzip_data *bd)
                    literal used is the one at the head of the mtfSymbol array.) */
                 if (runPos != 0) {
                         uint8_t tmp_byte;
-                        if (dbufCount + runCnt > dbufSize) {
-                                dbg("dbufCount:%d+runCnt:%d %d > dbufSize:%d RETVAL_DATA_ERROR",
-                                                dbufCount, runCnt, dbufCount + runCnt, dbufSize);
+                        if (dbufCount + runCnt > bd->dbufSize) {
+                                dbg("dbufCount:%u+runCnt:%u %u > dbufSize:%u RETVAL_DATA_ERROR",
+                                                dbufCount, runCnt, dbufCount + runCnt, bd->dbufSize);
                                 return RETVAL_DATA_ERROR;
                         }
                         tmp_byte = symToByte[mtfSymbol[0]];
                         byteCount[tmp_byte] += runCnt;
-                        while (--runCnt >= 0) dbuf[dbufCount++] = (uint32_t)tmp_byte;
+                        while ((int)--runCnt >= 0)
+                                dbuf[dbufCount++] = (uint32_t)tmp_byte;
                         runPos = 0;
                 }
 
@@ -466,7 +474,7 @@ static int get_next_block(bunzip_data *bd)
                    first symbol in the mtf array, position 0, would have been handled
                    as part of a run above.  Therefore 1 unused mtf position minus
                    2 non-literal nextSym values equals -1.) */
-                if (dbufCount >= dbufSize) return RETVAL_DATA_ERROR;
+                if (dbufCount >= bd->dbufSize) return RETVAL_DATA_ERROR;
                 i = nextSym - 1;
                 uc = mtfSymbol[i];