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From William A Rowe Jr <wr...@rowe-clan.net>
Subject Re: New segfault with 2.4.20 with mod_perl
Date Thu, 14 Apr 2016 18:25:04 GMT
The defect appears to be in t/protocol/TestProtocol/pseudo_http.pm...

First, the handler is registered using

  PerlProcessConnectionHandler TestProtocol::pseudo_http

so its activities are outside of the request handling phase.

Note that this logic has been broken, for a long time;

          <IfVersion > 2.4.1>
              <IfModule mod_access_compat.c>
                  Order Deny,Allow
                  Allow from @servername@
              </IfModule>
          </IfVersion>

Where @servername@ is a hostname, this module defect was
identified in version 2.4.20 when we began using the per-req
hostname in comparison (based on r->useragent_addr, which
is obviously is null during part of the read_request phase).

But this module using mod_access_compat during the connection
phase has been broken for much longer, since Allow from {ip-addr}
would already have failed since 2.4.1 was released, due to the
same null r->useragent_addr.

Effectively, mod_access_compat.c never supported per-connection
IP addresses since it was added.  The fact that it supported
per-connection hostname comparison was a quirk, and that the
pseudo_http tests only looked at hostname and not ip comparisons
was an oversight.

But the module will fail in other manners if attempting to use
http request_rec processing since that record is never fleshed
out with the proper read/post_read request hook phases.

My thought is to simply decouple access_compat from this
module test... opinions?

See also; https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=820824;msg=5


On Thu, Apr 14, 2016 at 11:55 AM, William A Rowe Jr <wrowe@rowe-clan.net>
wrote:

> We can be more vigilant about unexpectedly null values, however...
>
> how are you running request processing in the connection callback
> of mod_perl?  That makes no sense, and probably signals a deeper
> logic error.
>
> The access checker is configured per-dir, so until the request rec
> is completely initialized during read_request, this doesn't make
> much sense to me (full backtrace .. including frames #6-#10, for
> those who are curious...)
>
> Either the callback list registered for modperl_callback_connection,
> or the Perl_runops_standard, or the Perl_pp_entersub invoking the
> run_access_checker hook seem the most suspect here.
>
> #0  apr_getnameinfo (hostname=hostname@entry=0x7fd4461ee368, sockaddr=0x0, flags=flags@entry=0)
>     at /tmp/buildd/apr-1.5.2/network_io/unix/sockaddr.c:663
> #1  0x000055feaf0f513a in ap_get_useragent_host (r=r@entry=0x7fd4461ee0a0, type=type@entry=3,
>     str_is_ip=str_is_ip@entry=0x7fd44740c9c4) at core.c:990
> #2  0x00007fd4519d7212 in find_allowdeny (r=r@entry=0x7fd4461ee0a0, method=method@entry=0,
a=<optimized out>,
>     a=<optimized out>) at mod_access_compat.c:279
> #3  0x00007fd4519d74b2 in check_dir_access (r=0x7fd4461ee0a0) at mod_access_compat.c:332
> #4  0x000055feaf0f8f30 in ap_run_access_checker (r=r@entry=0x7fd4461ee0a0) at request.c:87
> #5  0x00007fd448a6f7dd in XS_Apache2__RequestRec_run_access_checker (my_perl=0x55feb2964a20,
cv=<optimized out>)
>     at HookRun.c:235
> #6  0x00007fd44f5f7e6a in Perl_pp_entersub () from /usr/lib/x86_64-linux-gnu/libperl.so.5.22
> #7  0x00007fd44f5f0ca6 in Perl_runops_standard () from /usr/lib/x86_64-linux-gnu/libperl.so.5.22
> #8  0x00007fd44f575f06 in Perl_call_sv () from /usr/lib/x86_64-linux-gnu/libperl.so.5.22
> #9  0x00007fd44f91ec28 in modperl_callback (my_perl=my_perl@entry=0x55feb2964a20, handler=0x7fd4461f2750,
>     p=p@entry=0x7fd4461f2028, r=r@entry=0x0, s=s@entry=0x7fd453ddc628, args=0x55feb3beebd0)
>     at modperl_callback.c:100
> #10 0x00007fd44f91f576 in modperl_callback_run_handlers (idx=0, type=type@entry=1, r=r@entry=0x0,
>     c=<optimized out>, s=0x7fd453ddc628, pconf=pconf@entry=0x0, plog=0x0, ptemp=0x0,
run_mode=MP_HOOK_RUN_FIRST)
>     at modperl_callback.c:236
> #11 0x00007fd44f91fd4f in modperl_callback_connection (idx=<optimized out>, c=<optimized
out>,
>     run_mode=<optimized out>) at modperl_callback.c:359
> #12 0x000055feaf10cdf0 in ap_run_process_connection (c=c@entry=0x7fd4461f22b8) at connection.c:42
> #13 0x000055feaf10d340 in ap_process_connection (c=c@entry=0x7fd4461f22b8, csd=csd@entry=0x7fd4461f20a0)
>     at connection.c:226
> #14 0x00007fd4523f3e6b in process_socket (bucket_alloc=0x7fd4461f0028, my_thread_num=1,
my_child_num=0,
>     sock=0x7fd4461f20a0, p=0x7fd4461f2028, thd=0x7fd453eb27a0) at worker.c:631
> #15 worker_thread (thd=0x7fd453eb27a0, dummy=<optimized out>) at worker.c:990
> #16 0x00007fd453418454 in start_thread (arg=0x7fd44740d700) at pthread_create.c:334
> #17 0x00007fd453155ecd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109
>
>
> Before we chase down a potential non-defect in httpd, any thoughts
> on the underlying modperl or script logic?
>
>
> On Thu, Apr 14, 2016 at 1:44 AM, Takashi Sato <takashi@tks.st> wrote:
>
>> r->useragent_addr is assigned on ap_read_request (http_core.c),
>> called from ap_process_http_(async_)connection
>> called from process_connection hook (APR_HOOK_REALLY_LAST).
>>
>> The SEGV occured on process_connection hook, maybe before
>> ap_process_http_(async_)connection,
>>
>> #11 0x00007fd44f91fd4f in modperl_callback_connection (idx=<optimized
>> out>, c=<optimized out>,
>>     run_mode=<optimized out>) at modperl_callback.c:359
>> #12 0x000055feaf10cdf0 in ap_run_process_connection
>> (c=c@entry=0x7fd4461f22b8) at connection.c:42
>> #13 0x000055feaf10d340 in ap_process_connection
>> (c=c@entry=0x7fd4461f22b8, csd=csd@entry=0x7fd4461f20a0)
>>     at connection.c:226
>>
>> so r->useragent_addr had not been assigned any value.
>>
>
>

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