[FFmpeg-devel] [PATCH] avformat/options_table: Set the default maximum number of streams to 100

Michael Niedermayer michael at niedermayer.cc
Fri Dec 9 03:44:11 EET 2016

On Thu, Dec 08, 2016 at 09:47:53PM +0100, Nicolas George wrote:
> L'octidi 18 frimaire, an CCXXV, Michael Niedermayer a écrit :
> > A. Is a heap limit for av_*alloc*() acceptable ?
> > B. Are case based limits acceptable ?
> No. This is the task of the operating system.

> > also even if C is choosen, a small set of limits on the main parameters
> > still is needed to allow efficient fuzzing, all issues reported
> > by oss-fuzz recently are "hangs" due to slow decoding,
> Then set a limit at the operating system level.

You are misunderstanding the problem i think

The goal of a fuzzer is to find bugs, crashes, undefined, bad things,
OOM, hangs.

If the code under test can allocate arbitrary amounts of memory and
take arbitrary amounts of time in a significant number of non-bug
cases then the fuzzer cannot reliably find the corresponding bugs.

moving the threshold of where to declare something OOM or hang around
will not solve this.
blocking high resolution, high channel count, high stream count
cases OTOH should improve the rate of false positives.

also, secondary, resources spent on waiting for hangs to separate from
slow decoding and real OOM to separate from cases just needing alot
of memory, are resources that could be used for other things like
fuzzing more seperate cases.

but either way, iam the wrong one to disscuss changes to oss-fuzz with
if you do have ideas that would improve it ...


Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

If you drop bombs on a foreign country and kill a hundred thousand
innocent people, expect your government to call the consequence
"unprovoked inhuman terrorist attacks" and use it to justify dropping
more bombs and killing more people. The technology changed, the idea is old.
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