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 <taka...@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. >