vp8enc: Prevent out of bounds memory access.

Prevent out of bounds access when attempting to increase frame size

Change-Id: I710c40c692802a72963c9680c2125da17f9060a9

vp8/encoder/onyx_if.c

diff --git a/vp8/encoder/onyx_if.c b/vp8/encoder/onyx_if.c
index 41b3066..258fa11 100644
--- a/vp8/encoder/onyx_if.c
+++ b/vp8/encoder/onyx_if.c
@@ -1760,8 +1760,16 @@
         reset_temporal_layer_change(cpi, oxcf, prev_number_of_layers);
     }
 
+    if (!cpi->initial_width)
+    {
+        cpi->initial_width = cpi->oxcf.Width;
+        cpi->initial_height = cpi->oxcf.Height;
+    }
+
     cm->Width       = cpi->oxcf.Width;
     cm->Height      = cpi->oxcf.Height;
+    assert(cm->Width <= cpi->initial_width);
+    assert(cm->Height <= cpi->initial_height);
 
     /* TODO(jkoleszar): if an internal spatial resampling is active,
      * and we downsize the input image, maybe we should clear the

vp8/encoder/onyx_int.h

diff --git a/vp8/encoder/onyx_int.h b/vp8/encoder/onyx_int.h
index b1a749c..82d7453 100644
--- a/vp8/encoder/onyx_int.h
+++ b/vp8/encoder/onyx_int.h
@@ -665,6 +665,9 @@
 
     int droppable;
 
+    int initial_width;
+    int initial_height;
+
 #if CONFIG_TEMPORAL_DENOISING
     VP8_DENOISER denoiser;
 #endif

vp8/vp8_cx_iface.c

diff --git a/vp8/vp8_cx_iface.c b/vp8/vp8_cx_iface.c
index f81f078..96b4cb5 100644
--- a/vp8/vp8_cx_iface.c
+++ b/vp8/vp8_cx_iface.c
@@ -447,9 +447,14 @@
 {
     vpx_codec_err_t res;
 
-    if (((cfg->g_w != ctx->cfg.g_w) || (cfg->g_h != ctx->cfg.g_h))
-        && (cfg->g_lag_in_frames > 1 || cfg->g_pass != VPX_RC_ONE_PASS))
-        ERROR("Cannot change width or height after initialization");
+    if (cfg->g_w != ctx->cfg.g_w || cfg->g_h != ctx->cfg.g_h)
+    {
+        if (cfg->g_lag_in_frames > 1 || cfg->g_pass != VPX_RC_ONE_PASS)
+            ERROR("Cannot change width or height after initialization");
+        if ((ctx->cpi->initial_width && (int)cfg->g_w > ctx->cpi->initial_width) ||
+            (ctx->cpi->initial_height && (int)cfg->g_h > ctx->cpi->initial_height))
+            ERROR("Cannot increast width or height larger than their initial values");
+    }
 
     /* Prevent increasing lag_in_frames. This check is stricter than it needs
      * to be -- the limit is not increasing past the first lag_in_frames