On Thu, 2 Feb 2017, Jacob Champion 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
Idle thoughts: "Cannot access memory" in this case could be a red herring, if
Niklas' gdb can't peer into mmap'd memory spaces [1]. It seems reasonable
that the data in question could be mmap'd, given the nice round address and 4
MiB length (equal to APR_MMAP_LIMIT).
Oooh, hadn't even though of that...
That doesn't mean we're looking in the wrong place, though, since SIGBUS can
also be generated by an out-of-bounds access to an mmap'd region.
Niklas, what version of APR are you using? Are you serving large (> 4 MiB)
static files? I have not been able to reproduce so far (Ubuntu 16.04, httpd
2.4.25 + mod_ssl + mpm_event).
Yes, this is a file archive offload target ONLY serving large files.
APR from httpd-2.4.25-deps.tar.bz2 and
./configure --prefix=/lap/apache/2.4.25.sslcleanuppatch
--sysconfdir=/var/conf/apache2 --with-included-apr
--enable-nonportable-atomics=yes --enable-layout=GNU --enable-mpms-shared=all
--with-gdbm --without-berkeley-db --enable-mods-shared=all
--enable-cache=shared --enable-cache-disk=shared --enable-ssl=shared
--enable-cgi=shared --enable-suexec --with-suexec-caller=www-srv
--with-suexec-uidmin=1000 --with-suexec-gidmin=1000 CFLAGS=-O2 -
(yes, the cgi/suexec stuff isn't really used but we haven't gotten around to
change our builds).
It's indeed using that APR according to
/proc/pid/maps, libapr-1.so.0.5.2 in the httpd install tree.
/Nikke
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