libavfilter: guard against ff_draw_init/ff_draw_init2 failures

The return value of ff_draw_init and ff_draw_init2 are not checked in
most usages. However, if they return an error, they don't get to the
point where they set the attributes of the FFDrawContext. These
functions are typically used in conjunction with ff_draw_color, which
checks draw->desc->flags, causing a null pointer dereference.

Signed-off-by: Nil Fons Miret <[email protected]>
Signed-off-by: Michael Niedermayer <[email protected]>

1 files changed, 25 insertions, 6 deletions

diff --git a/libavfilter/vf_datascope.c b/libavfilter/vf_datascope.c
index 75dc149fbd..6efeb875a6 100644
--- a/libavfilter/vf_datascope.c
+++ b/libavfilter/vf_datascope.c
@@ -382,11 +382,18 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *in)
 
 static int config_input(AVFilterLink *inlink)
 {
-    DatascopeContext *s = inlink->dst->priv;
+    AVFilterContext *ctx = inlink->dst;
+    DatascopeContext *s = ctx->priv;
+
     uint8_t alpha = s->opacity * 255;
+    int ret;
 
     s->nb_planes = av_pix_fmt_count_planes(inlink->format);
-    ff_draw_init2(&s->draw, inlink->format, inlink->colorspace, inlink->color_range, 0);
+    ret = ff_draw_init2(&s->draw, inlink->format, inlink->colorspace, inlink->color_range, 0);
+    if (ret < 0) {
+        av_log(ctx, AV_LOG_ERROR, "Failed to initialize FFDrawContext\n");
+        return ret;
+    }
     ff_draw_color(&s->draw, &s->white,  (uint8_t[]){ 255, 255, 255, 255} );
     ff_draw_color(&s->draw, &s->black,  (uint8_t[]){ 0, 0, 0, alpha} );
     ff_draw_color(&s->draw, &s->yellow, (uint8_t[]){ 255, 255, 0, 255} );
@@ -509,10 +516,16 @@ AVFILTER_DEFINE_CLASS(pixscope);
 
 static int pixscope_config_input(AVFilterLink *inlink)
 {
-    PixscopeContext *s = inlink->dst->priv;
+    AVFilterContext *ctx = inlink->dst;
+    PixscopeContext *s = ctx->priv;
+    int ret;
 
     s->nb_planes = av_pix_fmt_count_planes(inlink->format);
-    ff_draw_init(&s->draw, inlink->format, 0);
+    ret = ff_draw_init(&s->draw, inlink->format, 0);
+    if (ret < 0) {
+        av_log(ctx, AV_LOG_ERROR, "Failed to initialize FFDrawContext\n");
+        return ret;
+    }
     ff_draw_color(&s->draw, &s->dark,  (uint8_t[]){ 0, 0, 0, s->o * 255} );
     ff_draw_color(&s->draw, &s->black, (uint8_t[]){ 0, 0, 0, 255} );
     ff_draw_color(&s->draw, &s->white, (uint8_t[]){ 255, 255, 255, 255} );
@@ -927,11 +940,17 @@ static void update_oscilloscope(AVFilterContext *ctx)
 
 static int oscilloscope_config_input(AVFilterLink *inlink)
 {
-    OscilloscopeContext *s = inlink->dst->priv;
+    AVFilterContext *ctx = inlink->dst;
+    OscilloscopeContext *s = ctx->priv;
     int size;
+    int ret;
 
     s->nb_planes = av_pix_fmt_count_planes(inlink->format);
-    ff_draw_init(&s->draw, inlink->format, 0);
+    ret = ff_draw_init(&s->draw, inlink->format, 0);
+    if (ret < 0) {
+        av_log(ctx, AV_LOG_ERROR, "Failed to initialize FFDrawContext\n");
+        return ret;
+    }
     ff_draw_color(&s->draw, &s->black,   (uint8_t[]){   0,   0,   0, 255} );
     ff_draw_color(&s->draw, &s->white,   (uint8_t[]){ 255, 255, 255, 255} );
     ff_draw_color(&s->draw, &s->green,   (uint8_t[]){   0, 255,   0, 255} );