shithub: libvpx

Info  •  Files  •  Log  •  Branches

Prevent decoder from using uninitialized entropy context.

If decoding starts with intra-only frame, there is a possibility
of using uninitialized entropy context, what leads to undefined
behavior.

Change-Id: Icbb64b5b1bd1e5de2a4bfa2884e56bc0a20840af

--- a/vp9/common/vp9_entropymode.c

+++ b/vp9/common/vp9_entropymode.c

@@ -453,6 +453,7 @@

   vp9_default_coef_probs(cm);

   vp9_init_mode_probs(cm->fc);

   vp9_init_mv_probs(cm);

+  cm->fc->initialized = 1;

   if (cm->frame_type == KEY_FRAME ||

       cm->error_resilient_mode || cm->reset_frame_context == 3) {

--- a/vp9/common/vp9_entropymode.h

+++ b/vp9/common/vp9_entropymode.h

@@ -50,6 +50,7 @@

   struct tx_probs tx_probs;

   vp9_prob skip_probs[SKIP_CONTEXTS];

   nmv_context nmvc;

+  int initialized;

 } FRAME_CONTEXT;

 typedef struct {

--- a/vp9/decoder/vp9_decodeframe.c

+++ b/vp9/decoder/vp9_decodeframe.c

@@ -1558,6 +1558,10 @@

   vp9_setup_block_planes(xd, cm->subsampling_x, cm->subsampling_y);

   *cm->fc = cm->frame_contexts[cm->frame_context_idx];

+  if (!cm->fc->initialized)

+    vpx_internal_error(&cm->error, VPX_CODEC_CORRUPT_FRAME,

+                       "Uninitialized entropy context.");

+

   vp9_zero(cm->counts);

   vp9_zero(xd->dqcoeff);