avcodec: Always use av_malloc to alloc extradata

And always pad it while at it.
Codecs always expect extradata to be aligned and padded.

Prevent memory corruption when memalign-hack is enabled.
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/codec/avcodec/audio.c

@@ -96,7 +96,7 @@ static void InitDecoderConfig( decoder_t *p_dec, AVCodecContext *p_context )
         if( i_size > 0 )
         {
             p_context->extradata =
-                malloc( i_size + FF_INPUT_BUFFER_PADDING_SIZE );
+                av_malloc( i_size + FF_INPUT_BUFFER_PADDING_SIZE );
             if( p_context->extradata )
             {
                 uint8_t *p_dst = p_context->extradata;
@@ -234,7 +234,7 @@ int InitAudioDec( decoder_t *p_dec, AVCodecContext *p_context,
     if( ffmpeg_OpenCodec( p_dec ) < 0 )
     {
         msg_Err( p_dec, "cannot open codec (%s)", p_sys->psz_namecodec );
-        free( p_sys->p_context->extradata );
+        av_free( p_sys->p_context->extradata );
         free( p_sys );
         return VLC_EGENERIC;
     }

modules/codec/avcodec/avcodec.c

@@ -359,7 +359,7 @@ static void CloseDecoder( vlc_object_t *p_this )
 
     if( p_sys->p_context )
     {
-        free( p_sys->p_context->extradata );
+        av_free( p_sys->p_context->extradata );
         p_sys->p_context->extradata = NULL;
 
         if( !p_sys->b_delayed_open )

modules/codec/avcodec/video.c

@@ -790,8 +790,9 @@ static void ffmpeg_InitCodec( decoder_t *p_dec )
         uint8_t *p;
 
         p_sys->p_context->extradata_size = i_size + 12;
-        p = p_sys->p_context->extradata  =
-            malloc( p_sys->p_context->extradata_size );
+        p = p_sys->p_context->extradata =
+            av_malloc( p_sys->p_context->extradata_size +
+                       FF_INPUT_BUFFER_PADDING_SIZE );
         if( !p )
             return;
 
@@ -828,12 +829,12 @@ static void ffmpeg_InitCodec( decoder_t *p_dec )
     {
         p_sys->p_context->extradata_size = i_size;
         p_sys->p_context->extradata =
-            malloc( i_size + FF_INPUT_BUFFER_PADDING_SIZE );
+            av_malloc( i_size + FF_INPUT_BUFFER_PADDING_SIZE );
         if( p_sys->p_context->extradata )
         {
             memcpy( p_sys->p_context->extradata,
                     p_dec->fmt_in.p_extra, i_size );
-            memset( &((uint8_t*)p_sys->p_context->extradata)[i_size],
+            memset( p_sys->p_context->extradata + i_size,
                     0, FF_INPUT_BUFFER_PADDING_SIZE );
         }
     }