avcodec/hevc: Simplify get_qPy_pred()

Fixes use of uninitialized memory
Fixes: 93728afd9aa074ba14a09bfd93a632fd-asan_static-oob_124a17d_1445_cov_1021181966_DBLK_D_VIXS_1.bit
Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

1 files changed, 15 insertions, 1 deletions

diff --git a/libavcodec/hevc.c b/libavcodec/hevc.c
index 903157119a..545e737ba9 100644
--- a/libavcodec/hevc.c
+++ b/libavcodec/hevc.c
@@ -1634,6 +1634,7 @@ static int hls_coding_unit(HEVCContext *s, int x0, int y0, int log2_cb_size)
     int x_cb             = x0 >> log2_min_cb_size;
     int y_cb             = y0 >> log2_min_cb_size;
     int x, y, ret;
+    int qp_block_mask = (1<<(s->sps->log2_ctb_size - s->pps->diff_cu_qp_delta_depth)) - 1;
 
     lc->cu.x                = x0;
     lc->cu.y                = y0;
@@ -1771,6 +1772,11 @@ static int hls_coding_unit(HEVCContext *s, int x0, int y0, int log2_cb_size)
         x += min_cb_width;
     }
 
+    if(((x0 + (1<<log2_cb_size)) & qp_block_mask) == 0 &&
+       ((y0 + (1<<log2_cb_size)) & qp_block_mask) == 0) {
+        lc->qPy_pred = lc->qp_y;
+    }
+
     set_ct_depth(s, x0, y0, log2_cb_size, lc->ct.depth);
 
     return 0;
@@ -1782,6 +1788,7 @@ static int hls_coding_quadtree(HEVCContext *s, int x0, int y0,
     HEVCLocalContext *lc = s->HEVClc;
     const int cb_size    = 1 << log2_cb_size;
     int ret;
+    int qp_block_mask = (1<<(s->sps->log2_ctb_size - s->pps->diff_cu_qp_delta_depth)) - 1;
 
     lc->ct.depth = cb_depth;
     if (x0 + cb_size <= s->sps->width  &&
@@ -1822,8 +1829,15 @@ static int hls_coding_quadtree(HEVCContext *s, int x0, int y0,
         }
         if (more_data && x1 < s->sps->width &&
             y1 < s->sps->height) {
-            return hls_coding_quadtree(s, x1, y1, log2_cb_size - 1, cb_depth + 1);
+            more_data = hls_coding_quadtree(s, x1, y1, log2_cb_size - 1, cb_depth + 1);
+            if (more_data < 0)
+                return more_data;
         }
+
+        if(((x0 + (1<<log2_cb_size)) & qp_block_mask) == 0 &&
+            ((y0 + (1<<log2_cb_size)) & qp_block_mask) == 0)
+            lc->qPy_pred = lc->qp_y;
+
         if (more_data)
             return ((x1 + cb_size_split) < s->sps->width ||
                     (y1 + cb_size_split) < s->sps->height);