[FFmpeg-cvslog] avformat/webpenc: Check filesize in trailer

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Thu Jul 11 22:13:42 2024 +0200| [7734c583f777fdba2f6463cf525385ebe5cf10db] | committer: Michael Niedermayer

avformat/webpenc: Check filesize in trailer

not sure this is possible

Fixes: CID1604446 Overflowed constant

Sponsored-by: Sovereign Tech Fund
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=7734c583f777fdba2f6463cf525385ebe5cf10db
---

 libavformat/webpenc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavformat/webpenc.c b/libavformat/webpenc.c
index 1c5b93e0ab..ce0d046aa9 100644
--- a/libavformat/webpenc.c
+++ b/libavformat/webpenc.c
@@ -190,7 +190,7 @@ static int webp_write_trailer(AVFormatContext *s)
 
         if (!ret) {
             filesize = avio_tell(s->pb);
-            if (avio_seek(s->pb, 4, SEEK_SET) == 4) {
+            if (filesize >= 8 && avio_seek(s->pb, 4, SEEK_SET) == 4) {
                 avio_wl32(s->pb, filesize - 8);
                 // Note: without the following, avio only writes 8 bytes to the file.
                 avio_seek(s->pb, filesize, SEEK_SET);