[FFmpeg-devel] Fix memset size on ctts_data in mov_read_trun()
Michael Niedermayer
michael at niedermayer.cc
Tue Feb 27 12:38:58 EET 2018
On Mon, Feb 26, 2018 at 10:37:51AM -0800, Xiaohan Wang (王消寒) wrote:
> Thanks! Updated the patch. Please take a look again.
>
> On Sat, Feb 24, 2018 at 7:04 PM, Michael Niedermayer <michael at niedermayer.cc
> > wrote:
>
> > On Fri, Feb 23, 2018 at 05:12:05PM -0800, Xiaohan Wang (王消寒) wrote:
> > > Michael: Dale and I dig into history a bit more and we don't understand
> > why
> > > the code is changed to the current state around memset. This new patch
> > > reverted the change back to the previous state which we felt is much
> > > cleaner. Please see the CL description for details and take a look at the
> > > new patch. Thanks!
> > >
> > > On Wed, Feb 21, 2018 at 1:14 PM, Xiaohan Wang (王消寒) <xhwang at chromium.org
> > >
> > > wrote:
> > >
> > > > jstebbins: kindly ping!
> > > >
> > > > On Fri, Feb 16, 2018 at 2:42 PM, Xiaohan Wang (王消寒) <
> > xhwang at chromium.org>
> > > > wrote:
> > > >
> > > >> +jstebbins@ who wrote that code.
> > > >>
> > > >> On Fri, Feb 16, 2018 at 12:30 PM, Michael Niedermayer <
> > > >> michael at niedermayer.cc> wrote:
> > > >>
> > > >>> On Thu, Feb 15, 2018 at 12:10:33PM -0800, Xiaohan Wang (王消寒) wrote:
> > > >>> >
> > > >>>
> > > >>> > mov.c | 3 ++-
> > > >>> > 1 file changed, 2 insertions(+), 1 deletion(-)
> > > >>> > 5597d0b095f8b15eb11503010a51c2bc2c022413
> > > >>> 0001-ffmpeg-Fix-memset-size-on-ctts_data-in-mov_read_trun.patch
> > > >>> > From 7c1e6b50ebe35b2a38c4f1d0a988e31eccbd0ead Mon Sep 17 00:00:00
> > 2001
> > > >>> > From: Xiaohan Wang <xhwang at chromium.org>
> > > >>> > Date: Thu, 15 Feb 2018 12:05:53 -0800
> > > >>> > Subject: [PATCH] ffmpeg: Fix memset size on ctts_data in
> > > >>> mov_read_trun()
> > > >>> >
> > > >>> > The allocated size of sc->ctts_data is
> > > >>> > (st->nb_index_entries + entries) * sizeof(*sc->ctts_data).
> > > >>> >
> > > >>> > The size to memset at offset sc->ctts_data + sc->ctts_count should
> > be
> > > >>> > (st->nb_index_entries + entries - sc->ctts_count) *
> > > >>> sizeof(*sc->ctts_data))
> > > >>> >
> > > >>> > The current code missed |entries| I believe.
> > > >>>
> > > >>> shouldnt "entries" be read by this function later and so shouldnt
> > need a
> > > >>> memset?
> > > >>> I didnt write this, but it looks a bit to me as if it was intended to
> > > >>> only
> > > >>> clear the area that would not be read later
> > > >>>
> > > >>
> > > >> I thought we only had sc->ctts_count entries before av_fast_realloc,
> > so
> > > >> memset everything starting from sc->ctts_data + sc->ctts_count
> > couldn't
> > > >> go wrong. But I am not familiar with this code and that could totally
> > be
> > > >> wrong. I added jstebbins@ who wrote the code and hopefully we can get
> > > >> expert opinion there.
> > > >>
> > > >>
> > > >>> [...]
> > > >>> --
> > > >>> Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC7
> > 87040B0FAB
> > > >>>
> > > >>> No great genius has ever existed without some touch of madness. --
> > > >>> Aristotle
> > > >>>
> > > >>> _______________________________________________
> > > >>> ffmpeg-devel mailing list
> > > >>> ffmpeg-devel at ffmpeg.org
> > > >>> http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> > > >>>
> > > >>>
> > > >>
> > > >
> >
> > > mov.c | 5 +++--
> > > 1 file changed, 3 insertions(+), 2 deletions(-)
> > > e5bbe55f0b1260f787f431b5c45e6ca49a7d2d1e 0001-Fix-memset-size-on-ctts_
> > data-in-mov_read_trun-round-.patch
> > > From f34b35ec5749c17b21f80665a0b8859bce3e84ab Mon Sep 17 00:00:00 2001
> > > From: Xiaohan Wang <xhwang at chromium.org>
> > > Date: Fri, 23 Feb 2018 10:51:30 -0800
> > > Subject: [PATCH] Fix memset size on ctts_data in mov_read_trun() (round
> > 2)
> > >
> > > The allocated size of sc->ctts_data is
> > > (st->nb_index_entries + entries) * sizeof(*sc->ctts_data).
> > >
> > > The size to memset at offset sc->ctts_data + sc->ctts_count should be
> > > (st->nb_index_entries + entries - sc->ctts_count) *
> > > sizeof(*sc->ctts_data))
> > >
> > > The current code missed |entries| I believe, which was introduced in
> > > https://patchwork.ffmpeg.org/patch/5541/.
> > >
> > > However, after offline discussion, it seems the original code is much
> > > more clear to read (before https://patchwork.ffmpeg.org/patch/5541/).
> > >
> > > Hence this CL revert the memset logic to it's previous state by
> > > remembering the |old_ctts_allocated_size|, and only memset the newly
> > > allocated entries.
> > > ---
> > > libavformat/mov.c | 5 +++--
> > > 1 file changed, 3 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/libavformat/mov.c b/libavformat/mov.c
> > > index a3725692a7..f8d79c7b02 100644
> > > --- a/libavformat/mov.c
> > > +++ b/libavformat/mov.c
> > > @@ -4713,6 +4713,7 @@ static int mov_read_trun(MOVContext *c,
> > AVIOContext *pb, MOVAtom atom)
> > > st->index_entries= new_entries;
> > >
> > > requested_size = (st->nb_index_entries + entries) *
> > sizeof(*sc->ctts_data);
> > > + unsigned int old_ctts_allocated_size = sc->ctts_allocated_size;
> >
> > this should possibly be size_t
> >
> > and declaration and statements should not be mixed
> >
> > libavformat/mov.c: In function ‘mov_read_trun’:
> > libavformat/mov.c:4691:5: warning: ISO C90 forbids mixed declarations and
> > code [-Wdeclaration-after-statement]
> >
> > [...]
> >
> > --
> > Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
> >
> > If you fake or manipulate statistics in a paper in physics you will never
> > get a job again.
> > If you fake or manipulate statistics in a paper in medicin you will get
> > a job for life at the pharma industry.
> >
> > _______________________________________________
> > ffmpeg-devel mailing list
> > ffmpeg-devel at ffmpeg.org
> > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> >
> >
> mov.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
> b6b9921ba048a72f86e49a5cbb14238ce5137ebb 0001-ffmpeg-Fix-memset-size-on-ctts_data-in-mov_read_trun.patch
> From 51fc5d4e25c128f260ce519ac85dc81313b48459 Mon Sep 17 00:00:00 2001
> From: Xiaohan Wang <xhwang at chromium.org>
> Date: Fri, 23 Feb 2018 17:04:41 -0800
> Subject: [PATCH] ffmpeg: Fix memset size on ctts_data in mov_read_trun()
> (round 2)
>
> The allocated size of sc->ctts_data is
> (st->nb_index_entries + entries) * sizeof(*sc->ctts_data).
>
> The size to memset at offset sc->ctts_data + sc->ctts_count should be
> (st->nb_index_entries + entries - sc->ctts_count) *
> sizeof(*sc->ctts_data))
>
> The current code missed |entries| I believe, which was introduced in
> https://patchwork.ffmpeg.org/patch/5541/.
>
> However, after offline discussion, it seems the original code is much
> more clear to read (before https://patchwork.ffmpeg.org/patch/5541/).
>
> Hence this CL revert the memset logic to it's previous state by
> remembering the |old_ctts_allocated_size|, and only memset the newly
> allocated entries.
>
> BUG=812567
>
> Change-Id: Ibe94c7138e5818bfaae76866bfa6619a9b8a2b6b
> Reviewed-on: https://chromium-review.googlesource.com/934925
> Reviewed-by: Dale Curtis <dalecurtis at chromium.org>
> ---
> libavformat/mov.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/libavformat/mov.c b/libavformat/mov.c
> index a3725692a7..c93ad7de67 100644
> --- a/libavformat/mov.c
> +++ b/libavformat/mov.c
> @@ -4621,6 +4621,7 @@ static int mov_read_trun(MOVContext *c, AVIOContext *pb, MOVAtom atom)
> int64_t prev_dts = AV_NOPTS_VALUE;
> int next_frag_index = -1, index_entry_pos;
> size_t requested_size;
> + size_t old_ctts_allocated_size = 0;
the assignment of 0 seems redundant
[...]
--
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
If you fake or manipulate statistics in a paper in physics you will never
get a job again.
If you fake or manipulate statistics in a paper in medicin you will get
a job for life at the pharma industry.
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