avfilter/src_movie: fix how we check for overflows with seek_point
authorMarios Titas <redneb@gmx.com>
Sat, 2 Apr 2016 18:11:44 +0000 (21:11 +0300)
committerMichael Niedermayer <michael@niedermayer.cc>
Thu, 28 Apr 2016 01:47:13 +0000 (03:47 +0200)
Currently, if the movie source filter is used and a seek_point is
specified on a file that has a negative start time, ffmpeg will fail.

An easy way to reproduce this is as follows:
$ ffmpeg -vsync passthrough -filter_complex 'color=d=10,setpts=PTS-1/TB' test.mp4
$ ffmpeg -filter_complex 'movie=filename=test.mp4:seek_point=2' -f null -

The problem is caused by checking for int64_t overflow the wrong way.
In general, to check whether a + b overflows, it is not enough to do:
    a > INT64_MAX - b
because b might be negative; the correct way is:
    b > 0 && > a > INT64_MAX - b

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit c1f9734f977f59bc0034096afbe8e43e40d93a5d)

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
libavfilter/src_movie.c

index 908c03e..6df52f7 100644 (file)
@@ -240,7 +240,7 @@ static av_cold int movie_common_init(AVFilterContext *ctx)
         timestamp = movie->seek_point;
         // add the stream start time, should it exist
         if (movie->format_ctx->start_time != AV_NOPTS_VALUE) {
-            if (timestamp > INT64_MAX - movie->format_ctx->start_time) {
+            if (timestamp > 0 && movie->format_ctx->start_time > INT64_MAX - timestamp) {
                 av_log(ctx, AV_LOG_ERROR,
                        "%s: seek value overflow with start_time:%"PRId64" seek_point:%"PRId64"\n",
                        movie->file_name, movie->format_ctx->start_time, movie->seek_point);