From 3819db745da2ac7fb3faacb116788c32f4753f34 Mon Sep 17 00:00:00 2001
From: Michael Niedermayer <michaelni@gmx.at>
Date: Thu, 22 Aug 2013 01:07:32 +0200
Subject: [PATCH] avcodec/rpza: Perform pointer advance and checks before using
 the pointers

Fixes out of array accesses
Fixes Ticket2850

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
---
 libavcodec/rpza.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/libavcodec/rpza.c b/libavcodec/rpza.c
index 2aa0091d32..416f8b6722 100644
--- a/libavcodec/rpza.c
+++ b/libavcodec/rpza.c
@@ -85,7 +85,7 @@ static void rpza_decode_stream(RpzaContext *s)
     unsigned short *pixels = (unsigned short *)s->frame.data[0];
 
     int row_ptr = 0;
-    int pixel_ptr = 0;
+    int pixel_ptr = -4;
     int block_ptr;
     int pixel_x, pixel_y;
     int total_blocks;
@@ -141,6 +141,7 @@ static void rpza_decode_stream(RpzaContext *s)
             colorA = AV_RB16 (&s->buf[stream_ptr]);
             stream_ptr += 2;
             while (n_blocks--) {
+                ADVANCE_BLOCK()
                 block_ptr = row_ptr + pixel_ptr;
                 for (pixel_y = 0; pixel_y < 4; pixel_y++) {
                     for (pixel_x = 0; pixel_x < 4; pixel_x++){
@@ -149,7 +150,6 @@ static void rpza_decode_stream(RpzaContext *s)
                     }
                     block_ptr += row_inc;
                 }
-                ADVANCE_BLOCK();
             }
             break;
 
@@ -188,6 +188,7 @@ static void rpza_decode_stream(RpzaContext *s)
             if (s->size - stream_ptr < n_blocks * 4)
                 return;
             while (n_blocks--) {
+                ADVANCE_BLOCK();
                 block_ptr = row_ptr + pixel_ptr;
                 for (pixel_y = 0; pixel_y < 4; pixel_y++) {
                     index = s->buf[stream_ptr++];
@@ -198,7 +199,6 @@ static void rpza_decode_stream(RpzaContext *s)
                     }
                     block_ptr += row_inc;
                 }
-                ADVANCE_BLOCK();
             }
             break;
 
@@ -206,6 +206,7 @@ static void rpza_decode_stream(RpzaContext *s)
         case 0x00:
             if (s->size - stream_ptr < 16)
                 return;
+            ADVANCE_BLOCK();
             block_ptr = row_ptr + pixel_ptr;
             for (pixel_y = 0; pixel_y < 4; pixel_y++) {
                 for (pixel_x = 0; pixel_x < 4; pixel_x++){
@@ -219,7 +220,6 @@ static void rpza_decode_stream(RpzaContext *s)
                 }
                 block_ptr += row_inc;
             }
-            ADVANCE_BLOCK();
             break;
 
         /* Unknown opcode */