[FFmpeg-devel] [PATCH v2 1/3] fftools/ffmpeg_filter: fix NULL pointer dereference

[Zhao Zhili]

From: Zhao Zhili <zhilizhao at tencent.com>

In close_output(), a dummy frame is created with format NONE passed
to enc_open(), which doesn't prepare for it. The NULL pointer
dereference happened at
av_pix_fmt_desc_get(enc_ctx->pix_fmt)->comp[0].depth.

When fgt.graph is NULL, skip fg_output_frame() since there is
nothing to output.

frame #0: 0x0000005555bc34a4 ffmpeg_g`enc_open(opaque=0xb400007efe2db690, frame=0xb400007efe2d9f70) at ffmpeg_enc.c:235:44
frame #1: 0x0000005555bef250 ffmpeg_g`enc_open(sch=0xb400007dde2d4090, enc=0xb400007e4e2daad0, frame=0xb400007efe2d9f70) at ffmpeg_sched.c:1462:11
frame #2: 0x0000005555bee094 ffmpeg_g`send_to_enc(sch=0xb400007dde2d4090, enc=0xb400007e4e2daad0, frame=0xb400007efe2d9f70) at ffmpeg_sched.c:1571:19
frame #3: 0x0000005555bee01c ffmpeg_g`sch_filter_send(sch=0xb400007dde2d4090, fg_idx=0, out_idx=0, frame=0xb400007efe2d9f70) at ffmpeg_sched.c:2154:12
frame #4: 0x0000005555bcf124 ffmpeg_g`close_output(ofp=0xb400007e4e2d85b0, fgt=0x0000007d1790eb08) at ffmpeg_filter.c:2225:15
frame #5: 0x0000005555bcb000 ffmpeg_g`fg_output_frame(ofp=0xb400007e4e2d85b0, fgt=0x0000007d1790eb08, frame=0x0000000000000000) at ffmpeg_filter.c:2317:16
frame #6: 0x0000005555bc7e48 ffmpeg_g`filter_thread(arg=0xb400007eae2ce7a0) at ffmpeg_filter.c:2836:15
frame #7: 0x0000005555bee568 ffmpeg_g`task_wrapper(arg=0xb400007d8e2db478) at ffmpeg_sched.c:2200:21
---
 fftools/ffmpeg_filter.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/fftools/ffmpeg_filter.c b/fftools/ffmpeg_filter.c
index 9fc877b437..69a49a071e 100644
--- a/fftools/ffmpeg_filter.c
+++ b/fftools/ffmpeg_filter.c
@@ -2335,10 +2335,7 @@ static int fg_output_step(OutputFilterPriv *ofp, FilterGraphThread *fgt,
 
     ret = av_buffersink_get_frame_flags(filter, frame,
                                         AV_BUFFERSINK_FLAG_NO_REQUEST);
-    if (ret == AVERROR_EOF && !fgt->eof_out[ofp->index]) {
-        ret = fg_output_frame(ofp, fgt, NULL);
-        return (ret < 0) ? ret : 1;
-    } else if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
+    if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
         return 1;
     } else if (ret < 0) {
         av_log(fgp, AV_LOG_WARNING,
@@ -2835,7 +2832,7 @@ read_frames:
     for (unsigned i = 0; i < fg->nb_outputs; i++) {
         OutputFilterPriv *ofp = ofp_from_ofilter(fg->outputs[i]);
 
-        if (fgt.eof_out[i])
+        if (fgt.eof_out[i] || !fgt.graph)
             continue;
 
         ret = fg_output_frame(ofp, &fgt, NULL);
-- 
2.25.1