jwestfall at surrealistic
Jul 14, 2007, 8:03 AM
Post #1 of 1
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Re: [mythtv-commits] Ticket #3074: AvFormatDecoder and avformat double free crashes
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MythTV <mythtv[at]cvs.mythtv.org> wrote [07.14.07]:
> #3074: AvFormatDecoder and avformat double free crashes
> -----------------------+----------------------------------------------------
> Reporter: jwestfall | Owner: janne
> Type: defect | Status: new
> Priority: minor | Milestone: 0.21
> Component: mythtv | Version: head
> Severity: medium | Resolution:
> Mlocked: 0 |
> -----------------------+----------------------------------------------------
>
> Comment(by danielk):
>
> Janne, av_free has had a NULL pointer check for a very long time for those
> few libc's that aren't NULL pointer safe, and to support the memalign
> hack, which requires the NULL pointer check. (i.e. this wasn't any
> different then the bug report was made, the backtrace may be bad if
> compile time optimizations were enabled --release-type=profile, or if
> something is overwriting memory.)
>
I use --compile-type=debug, I would guess some memory corruption caused
ptr to become NULL during the crash.
My local patch to fix this is to replace the av_free
in AvFormatDecoder::CloseContext() with av_freep. This forces
ic->pb.buffer to NULL after its been free'd. Any additional attempts to
av_free it will hit the NULL check.
jim
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