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From Yann Ylavic <ylavic....@gmail.com>
Subject Re: httpd 2.4.25, mpm_event, ssl: segfaults
Date Thu, 02 Feb 2017 10:04:48 GMT
Hi Niklas,

On Wed, Feb 1, 2017 at 7:02 PM, Niklas Edmundsson <nikke@acc.umu.se> wrote:
>
> We've started to see spurious segfaults with httpd 2.4.25, mpm_event, ssl on
> Ubuntu 14.04LTS. Not frequent, but none the less happening.
>
> #4  ssl_io_filter_output (f=0x7f507013cfe0, bb=0x7f4f840be168) at
> ssl_engine_io.c:1746
>         data = 0x7f5075518000 <error: Cannot access memory at address
> 0x7f5075518000>
>         len = 4194304
>         bucket = 0x7f4f840b1ba8
>         status = <optimized out>
>         filter_ctx = 0x7f507013cf88
>         inctx = <optimized out>
>         outctx = 0x7f507013d008
>         rblock = APR_NONBLOCK_READ

I suspect some cleanup ordering issue happening in
ssl_io_filter_output(), when the EOC bucket is found.

>
> Are we hitting a corner case of process cleanup that plays merry hell with
> https/ssl, or are we just having bad luck? Ideas? Suggestions?

2.4.25 is eager to terminate/shutdown keepalive connections more
quickly (than previous versions) on graceful shutdown (e.g.
MaxConnectionsPerChild reached).

What might happen in ssl_io_filter_output() is that buffered output
data (already deleted but not cleared) end up being reused on
shutdown.

Could you please try the attached patch?


Regards,
Yann.

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