quic: Check RLE lengths

Avoid buffer overflows decoding images. On compression we compute
lengths till end of line so it won't cause regressions.
Proved by fuzzing the code.
Signed-off-by: Frediano Ziglio <freddy77@gmail.com>
Acked-by: Uri Lublin <uril@redhat.com>

common/quic_tmpl.c

@@ -563,7 +563,11 @@ static void FNAME_DECL(uncompress_row_seg)(const PIXEL * const prev_row,
 do_run:
         state->waitcnt = stopidx - i;
         run_index = i;
-        run_end = i + decode_state_run(encoder, state);
+        run_end = decode_state_run(encoder, state);
+        if (run_end < 0 || run_end > (end - i)) {
+            encoder->usr->error(encoder->usr, "wrong RLE\n");
+        }
+        run_end += i;
 
         for (; i < run_end; i++) {
             UNCOMPRESS_PIX_START(&cur_row[i]);