| Message ID | CAF1j9YM8Yk9Bau4HMRiko=WAttBZEUi2RyPQzAs3dw8Zf4qV3Q@mail.gmail.com |
|---|---|
| State | Superseded |
| Headers | show |
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@chromium.org> > wrote: > > > jstebbins: kindly ping! > > > > On Fri, Feb 16, 2018 at 2:42 PM, Xiaohan Wang (王消寒) <xhwang@chromium.org> > > wrote: > > > >> +jstebbins@ who wrote that code. > >> > >> On Fri, Feb 16, 2018 at 12:30 PM, Michael Niedermayer < > >> michael@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@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: 9FF2128B147EF6730BADF133611EC787040B0FAB > >>> > >>> No great genius has ever existed without some touch of madness. -- > >>> Aristotle > >>> > >>> _______________________________________________ > >>> ffmpeg-devel mailing list > >>> ffmpeg-devel@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@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] [...]
From f34b35ec5749c17b21f80665a0b8859bce3e84ab Mon Sep 17 00:00:00 2001 From: Xiaohan Wang <xhwang@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; ctts_data = av_fast_realloc(sc->ctts_data, &sc->ctts_allocated_size, requested_size); if (!ctts_data) @@ -4722,8 +4723,8 @@ static int mov_read_trun(MOVContext *c, AVIOContext *pb, MOVAtom atom) // In case there were samples without ctts entries, ensure they get // zero valued entries. This ensures clips which mix boxes with and // without ctts entries don't pickup uninitialized data. - memset(sc->ctts_data + sc->ctts_count, 0, - (st->nb_index_entries - sc->ctts_count) * sizeof(*sc->ctts_data)); + memset((uint8_t*)(sc->ctts_data) + old_ctts_allocated_size, 0, + sc->ctts_allocated_size - old_ctts_allocated_size); if (index_entry_pos < st->nb_index_entries) { // Make hole in index_entries and ctts_data for new samples -- 2.16.1.291.g4437f3f132-goog