From a105f52855d08e4ab1ed7306da8e32fc90d6d647 Mon Sep 17 00:00:00 2001
From: Michael Niedermayer <michael@niedermayer.cc>
Date: Sat, 14 Nov 2015 21:11:52 +0100
Subject: [PATCH] avcodec/error_resilience: avoid accessing previous or next
 frames tables beyond height

The height of tables can be rounded up for MBAFF but this does not imply that is also true
for the previous frames

Fixes out of array reads
Fixes: c106b36fa36db8ff8f3ed0c82be7bea2/asan_heap-oob_32699f0_6321_467b9a1d7e03d7cfd310b7e65dc53bcc.mov

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
---
 libavcodec/error_resilience.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/libavcodec/error_resilience.c b/libavcodec/error_resilience.c
index 2c741a4a16..5a75faddf5 100644
--- a/libavcodec/error_resilience.c
+++ b/libavcodec/error_resilience.c
@@ -381,14 +381,19 @@ static void guess_mv(ERContext *s)
 #define MV_UNCHANGED 1
     const int mb_stride = s->mb_stride;
     const int mb_width  = s->mb_width;
-    const int mb_height = s->mb_height;
+    int mb_height = s->mb_height;
     int i, depth, num_avail;
     int mb_x, mb_y, mot_step, mot_stride;
 
+    if (s->last_pic.f && s->last_pic.f->data[0])
+        mb_height = FFMIN(mb_height, (s->last_pic.f->height+15)>>4);
+    if (s->next_pic.f && s->next_pic.f->data[0])
+        mb_height = FFMIN(mb_height, (s->next_pic.f->height+15)>>4);
+
     set_mv_strides(s, &mot_step, &mot_stride);
 
     num_avail = 0;
-    for (i = 0; i < s->mb_num; i++) {
+    for (i = 0; i < mb_width * mb_height; i++) {
         const int mb_xy = s->mb_index2xy[i];
         int f = 0;
         int error = s->error_status_table[mb_xy];
@@ -413,7 +418,7 @@ static void guess_mv(ERContext *s)
 
     if ((!(s->avctx->error_concealment&FF_EC_GUESS_MVS)) ||
         num_avail <= mb_width / 2) {
-        for (mb_y = 0; mb_y < s->mb_height; mb_y++) {
+        for (mb_y = 0; mb_y < mb_height; mb_y++) {
             for (mb_x = 0; mb_x < s->mb_width; mb_x++) {
                 const int mb_xy = mb_x + mb_y * s->mb_stride;
                 int mv_dir = (s->last_pic.f && s->last_pic.f->data[0]) ? MV_DIR_FORWARD : MV_DIR_BACKWARD;
@@ -442,7 +447,7 @@ static void guess_mv(ERContext *s)
             int score_sum = 0;
 
             changed = 0;
-            for (mb_y = 0; mb_y < s->mb_height; mb_y++) {
+            for (mb_y = 0; mb_y < mb_height; mb_y++) {
                 for (mb_x = 0; mb_x < s->mb_width; mb_x++) {
                     const int mb_xy        = mb_x + mb_y * s->mb_stride;
                     int mv_predictor[8][2] = { { 0 } };
@@ -675,7 +680,7 @@ skip_last_mv:
         if (none_left)
             return;
 
-        for (i = 0; i < s->mb_num; i++) {
+        for (i = 0; i < mb_width * mb_height; i++) {
             int mb_xy = s->mb_index2xy[i];
             if (fixed[mb_xy])
                 fixed[mb_xy] = MV_FROZEN;