The formats API deals with lists of channel layouts, sample rates,
pixel formats and sample formats. These lists are refcounted in a way in
which the list structure itself contains pointers to all of its owners.
Furthermore, it is possible for a list to be not owned by anyone yet;
this status is temporary until the list has been attached to an owner.
Adding an owner to a list involves reallocating the list's list of
owners and can therefore fail.
In order to reduce the amount of checks and cleanup code for the users
of this API, the API is supposed to be lenient when faced with input
lists that are NULL and it is supposed to clean up if adding an owner
to a list fails, so that a simple use case like
list = ff_make_format_list(foo_fmts);
if ((ret = ff_formats_ref(list, &ctx->inputs[0]->out_formats)) < 0)
return ret;
needn't check whether list could be successfully allocated
(ff_formats_ref() return AVERROR(ENOMEM) if it couldn't) and it also
needn't free list if ff_formats_ref() couldn't add an owner for it.
But the cleaning up after itself was broken. The root cause was that
the refcount was decremented during unreferencing whether or not the
element to be unreferenced was actually an owner of the list or not.
This means that if the above sample code is continued by
if ((ret = ff_formats_ref(list, &ctx->inputs[1]->out_formats)) < 0)
return ret;
and that if an error happens at the second ff_formats_ref() call, the
automatic cleaning of list will decrement the refcount from 1 (the sole
owner of list at this moment is ctx->input[0]->out_formats) to 0 and so
the list will be freed; yet ctx->input[0]->out_formats still points to
the list and this will lead to a double free/use-after-free when
ctx->input[0] is freed later.
Presumably in order to work around such an issue, commit
93afb338a405eac0f9e7b092bc26603378bfcca6 restricted unreferencing to
lists with owners. This does not solve the root cause (the above example
is not fixed by this) at all, but it solves some crashs.
This commit fixes the API: The list's refcount is only decremented if
an owner is removed from the list of owners and not if the
unref-function is called with a pointer that is not among the owners of
the list. Furtermore, the requirement for the list to have owners is
dropped.
This implies that if the first call to ff_formats_ref() in the above
example fails, the refcount which is initially zero during unreferencing
is not modified, so that the list will be freed automatically in said
call to ff_formats_ref() as every list whose refcount reaches zero is.
If on the other hand, the second call to ff_formats_ref() is the first
to fail, the refcount would stay at one during the automatic
unreferencing in ff_formats_ref(). The list would later be freed when
its last (and in this case sole) owner (namely
ctx->inputs[0]->out_formats) gets unreferenced.
The issues described here for ff_formats_ref() also affected the other
functions of this API. E.g. ff_add_format() failed to clean up after
itself if adding an entry to an already existing list failed (the case
of a freshly allocated list was handled specially and this commit also
removes said code). E.g. ff_all_formats() inherited the flaw.
Reviewed-by: Nicolas George <george@nsup.org>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
(cherry picked from commit 2a471af50aab02e8bb062c84a5779c7de1952fc0)
The channel layouts accepted by ff_merge_channel_layouts() are of two
types: Ordinary channel layouts and generic channel layouts. These are
layouts that match all layouts with a certain number of channels.
Therefore parsing these channel layouts is not done in one go; instead
first the intersection of the ordinary layouts of the first input
list of channel layouts with the ordinary layouts of the second list is
determined, then the intersection of the ordinary layouts of the first
one and the generic layouts of the second one etc. In order to mark the
ordinary channel layouts that have already been matched as used they are
zeroed. The inner loop that does this is as follows:
for (j = 0; j < b->nb_channel_layouts; j++) {
if (a->channel_layouts[i] == b->channel_layouts[j]) {
ret->channel_layouts[ret_nb++] = a->channel_layouts[i];
a->channel_layouts[i] = b->channel_layouts[j] = 0;
}
}
(Here ret->channel_layouts is the array containing the intersection of
the two input arrays.)
Yet the problem with this code is that after a match has been found, the
loop continues the search with the new value a->channel_layouts[i].
The intention of zeroing these elements was to make sure that elements
already paired at this stage are ignored later. And while they are indeed
ignored when pairing ordinary and generic channel layouts later, it has
the exact opposite effect when pairing ordinary channel layouts.
To see this consider the channel layouts A B C D E and E D C B A. In the
first round, A and A will be paired and added to ret->channel_layouts.
In the second round, the input arrays are 0 B C D E and E D C B 0.
At first B and B will be matched and zeroed, but after doing so matching
continues, but this time it will search for 0, which will match with the
last entry of the second array. ret->channel_layouts now contains A B 0.
In the third round, C 0 0 will be added to ret->channel_layouts etc.
This gives a quadratic amount of elements, yet the amount of elements
allocated for said array is only the sum of the sizes of a and b.
This issue can e.g. be reproduced by
ffmpeg -f lavfi -i anullsrc=cl=7.1 \
-af 'aformat=cl=mono|stereo|2.1|3.0|4.0,aformat=cl=4.0|3.0|2.1|stereo|mono' \
-f null -
The fix is easy: break out of the inner loop after having found a match.
Reviewed-by: Nicolas George <george@nsup.org>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
(cherry picked from commit 4147f63d63358e5c1969bfe431ee08ca54f8434d)
ff_merge_formats(), ff_merge_samplerates() and ff_merge_channel_layouts()
share common semantics: If merging succeeds, a non-NULL pointer is
returned and both input lists (of type AVFilterFormats resp.
AVFilterChannelLayouts) are to be treated as if they had been freed;
the owners of the input parameters (if any) become owners of the
returned list. If merging does not succeed, NULL is returned and both
input lists are supposed to be unchanged.
The problem is that the functions did not abide by these semantics:
In case of reallocation failure, it is possible for these functions
to return NULL after having already freed one of the two input list.
This happens because sometimes the refs-array of the destined output
gets reallocated twice to its final size and if the second of these
reallocations fails, the first of the two inputs has already been freed
and its refs updated to point to the destined output which in this case
will be freed immediately so that all of the already updated pointers
are now dangling. This leads to use-after-frees and memory corruptions
lateron (when these owners get cleaned up, the lists they own get
unreferenced). Should the input lists don't have owners at all, the
caller (namely can_merge_formats() in avfiltergraph.c) thinks that both
the input lists are unchanged and need to be freed, leading to a double
free.
The solution to this is simple: Don't reallocate twice; do it just once.
This also saves a reallocation.
This commit fixes the issue behind Coverity issue #1452636. It might
also make Coverity realize that the issue has been fixed.
Reviewed-by: Nicolas George <george@nsup.org>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
(cherry picked from commit 195a25a7aba89d4fc040de63cbc6389abece393d)
Use perdefined micro __FUNCTION__ rather than hard coding function name
to fix wrong function name in error message.
Signed-off-by: Jun Zhao <jun.zhao@intel.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
Current code returned the number of channels as channel layout in that case,
and if nret is not set then unknown layouts are typically not supported.
Also use the common parsing code. Use a temporary workaround to parse an
unknown channel layout such as '13c', after a 1 year grace period only '13C'
will work.
Signed-off-by: Marton Balint <cus@passwd.hu>
Since the default in the libav fork is to only allow known layouts, making
unknown layouts allowed by default here can be a security risk for filters
directly merged from libav. However, usually it is simple to detect such cases,
use of av_get_channel_layout_nb_channels is a good indicator, so I suggest we
change this regardless.
See http://ffmpeg.org/pipermail/ffmpeg-devel/2016-November/203204.html.
This patch indirectly adds unknown channel layout support for filters where
query_formats is not specified:
abench
afifo
ainterleave
anullsink
apad
aperms
arealtime
aselect
asendcmd
asetnsamples
asetpts
asettb
ashowinfo
azmq
It introduces a query_formats callback for the asyncts filter, which only
supports known channel layouts since it is using libavresample.
And it removes .query_formats callback from filters where it was only there to
support unknown layouts, as this is now the default:
aloop
ametadata
anull
asidedata
asplit
atrim
Acked-by: Nicolas George <george@nsup.org>
Signed-off-by: Marton Balint <cus@passwd.hu>
* commit 'd12b5b2f135aade4099f4b26b0fe678656158c13':
build: Split test programs off into separate files
Some conversions done by: James Almer <jamrial@gmail.com>
Merged-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
This is a somewhat subtle failure that can occur when the realloc_array
fails in FORMATS_REF.
Signed-off-by: Ganesh Ajjanagadde <gajjanagadde@gmail.com>
Many of the functions from avfilter/formats can return errors, usually AVERROR(ENOMEM).
This propagates the return values.
All of these were found by using av_warn_unused_result, demonstrating its utility.
Tested with FATE. I am least sure of the changes to avfilter/filtergraph,
since I don't know what/how reduce_format is intended to behave and how it should
react to errors.
Fixes: CID 1325680, 1325679, 1325678.
Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Previous version Reviewed-by: Nicolas George <george@nsup.org>
Previous version Reviewed-by: Clément Bœsch <u@pkh.me>
Signed-off-by: Ganesh Ajjanagadde <gajjanagadde@gmail.com>
* commit 'ae25413daf42a06f078ed81bb545ec23a8e0b482':
lavfi: do not exclude hwaccel formats from ff_all_formats()
Merged-by: Hendrik Leppkes <h.leppkes@gmail.com>
Also only free it when it was not previously allocated to return to the
state prior to the failing function call
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
The following commit:
b97d61f avfilter/ff_merge_formats: only merge if doing so does not loose chroma or alpha
introduced an exception to avoid lossy conversions.
Add a comment to explain the logic.
Fix the call to avoid applying it on audio formats.
