avformat/s337m: fix potentially undefined pointer arithmetic

Use integer position instead of pointer for loop variable. Also only skip header fields after header has been fully validated.

foo86 committed 9 years ago

Commit 6029b8a1 parent 5e715b51 file · +10 −10Browse files

Showing the changes to libavformat (1 of 1 file). Show all

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 {
     uint64_t state = 0;
     int markers[3] = { 0 };
-    int i, sum, max, data_type, data_size, offset;
+    int i, pos, sum, max, data_type, data_size, offset;
     uint8_t *buf;
-    for (buf = p->buf; buf < p->buf + p->buf_size; buf++) {
+    for (pos = 0; pos < p->buf_size; pos++) {
-        state = (state << 8) | *buf;
+        state = (state << 8) | p->buf[pos];
         if (!IS_LE_MARKER(state))
             continue;
+        buf = p->buf + pos + 1;
         if (IS_16LE_MARKER(state)) {
-            data_type = AV_RL16(buf + 1);
+            data_type = AV_RL16(buf    );
-            data_size = AV_RL16(buf + 3);
+            data_size = AV_RL16(buf + 2);
-            buf += 4;
         } else {
-            data_type = AV_RL24(buf + 1);
+            data_type = AV_RL24(buf    );
-            data_size = AV_RL24(buf + 4);
+            data_size = AV_RL24(buf + 3);
-            buf += 6;
         }
         if (s337m_get_offset_and_codec(NULL, state, data_type, data_size, &offset, NULL))
         i = IS_16LE_MARKER(state) ? 0 : IS_20LE_MARKER(state) ? 1 : 2;
         markers[i]++;
-        buf  += offset;
+        pos  += IS_16LE_MARKER(state) ? 4 : 6;
+        pos  += offset;
         state = 0;
     }

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