[FFmpeg-devel] [PATCH] ffprobe: fix use of uninitialized variable

[Zhao Zhili]

On Wed, Aug 9, 2017 at 1:23 AM, Michael Niedermayer <michael at niedermayer.cc>
wrote:

> On Sun, Aug 06, 2017 at 03:39:07PM +0800, Zhao Zhili wrote:
> > ---
> >  ffprobe.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/ffprobe.c b/ffprobe.c
> > index f22c4f57ad..ac9ff051fa 100644
> > --- a/ffprobe.c
> > +++ b/ffprobe.c
> > @@ -3328,6 +3328,7 @@ static int parse_read_interval(const char
> > *interval_spec,
> >              }
> >              interval->end = lli;
> >          } else {
> > +            interval->duration_frames = 0;
> >              ret = av_parse_time(&us, p, 1);
> >              if (ret < 0) {
> >                  av_log(NULL, AV_LOG_ERROR, "Invalid interval
> end/duration
> > specification '%s'\n", p);
> > @@ -3337,6 +3338,7 @@ static int parse_read_interval(const char
> > *interval_spec,
> >          }
> >      } else {
> >          interval->has_end = 0;
> > +        interval->duration_frames = 0;
> >      }
> >
> >  end:
> > @@ -3357,7 +3359,7 @@ static int parse_read_intervals(const char
> > *intervals_spec)
> >              n++;
> >      n++;
> >
> > -    read_intervals = av_malloc_array(n, sizeof(*read_intervals));
> > +    read_intervals = av_mallocz_array(n, sizeof(*read_intervals));
> >      if (!read_intervals) {
> >          ret = AVERROR(ENOMEM);
> >          goto end;
> > --
> > 2.13.2
>
> >  ffprobe.c |    4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 59efe1bf808d9621c14252fd0e71dc4b9a635c7a  0001-ffprobe-fix-use-of-
> uninitialized-variable.patch
> > From 1d3fe1eb4cd27efc337a1fae302f5539e3c7459b Mon Sep 17 00:00:00 2001
> > From: Zhao Zhili <wantlamy at gmail.com>
> > Date: Sun, 6 Aug 2017 15:33:42 +0800
> > Subject: [PATCH] ffprobe: fix use of uninitialized variable
> >
> > ---
> >  ffprobe.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/ffprobe.c b/ffprobe.c
> > index f22c4f57ad..ac9ff051fa 100644
> > --- a/ffprobe.c
> > +++ b/ffprobe.c
> > @@ -3328,6 +3328,7 @@ static int parse_read_interval(const char
> *interval_spec,
> >              }
> >              interval->end = lli;
> >          } else {
> > +            interval->duration_frames = 0;
> >              ret = av_parse_time(&us, p, 1);
> >              if (ret < 0) {
> >                  av_log(NULL, AV_LOG_ERROR, "Invalid interval
> end/duration specification '%s'\n", p);
>
> > @@ -3337,6 +3338,7 @@ static int parse_read_interval(const char
> *interval_spec,
> >          }
> >      } else {
> >          interval->has_end = 0;
> > +        interval->duration_frames = 0;
> >      }
>
> isnt has_end and end_is_offset 0 here and all uses of duration_frames
> under code checking either ?
>
>
If end_is_offset is 1 and *p is not '#', then duration_frames is not
initialized. So check end_is_offset doesn't prevent access uninitialized
value. And the current code didn't always check end_is_offset before access
duration_frames.

A simple test case:
ffprobe -show_frames -select_streams v -read_intervals '%+60' foo



>
> [...]
>
> --
> Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
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>
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