avformat/ffmdec: Check pix_fmt

Fixes crash
Fixes Ticket5412
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit 78baa450)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/ffmdec.c

@@ -26,6 +26,7 @@
 #include "libavutil/opt.h"
 #include "libavutil/avassert.h"
 #include "libavutil/avstring.h"
+#include "libavutil/pixdesc.h"
 #include "avformat.h"
 #include "internal.h"
 #include "ffm.h"
@@ -365,6 +366,11 @@ static int ffm2_read_header(AVFormatContext *s)
             codec->height = avio_rb16(pb);
             codec->gop_size = avio_rb16(pb);
             codec->pix_fmt = avio_rb32(pb);
+            if (!av_pix_fmt_desc_get(codec->pix_fmt)) {
+                av_log(s, AV_LOG_ERROR, "Invalid pix fmt id: %d\n", codec->pix_fmt);
+                codec->pix_fmt = AV_PIX_FMT_NONE;
+                goto fail;
+            }
             codec->qmin = avio_r8(pb);
             codec->qmax = avio_r8(pb);
             codec->max_qdiff = avio_r8(pb);
@@ -556,6 +562,11 @@ static int ffm_read_header(AVFormatContext *s)
             codec->height = avio_rb16(pb);
             codec->gop_size = avio_rb16(pb);
             codec->pix_fmt = avio_rb32(pb);
+            if (!av_pix_fmt_desc_get(codec->pix_fmt)) {
+                av_log(s, AV_LOG_ERROR, "Invalid pix fmt id: %d\n", codec->pix_fmt);
+                codec->pix_fmt = AV_PIX_FMT_NONE;
+                goto fail;
+            }
             codec->qmin = avio_r8(pb);
             codec->qmax = avio_r8(pb);
             codec->max_qdiff = avio_r8(pb);