fastcgi_cache_purge line in config causes segmentation fault since 1.7.8 in nginx-extras

[talkingnews]

Hello;

for many months I've been running the config shown here:
https://rtcamp.com/wordpress-nginx/tutorials/single-site/fastcgi-cache-with-purging/

This morning, I apt-get upgraded and got nginx 1.7.8 and a load of dead
sites. running nginx -t gave me a segmentation fault (core dumped) error.

After a whole load of panicking and commenting one line out at a time, I
finally tracked it down to this section:

location ~ /purge(/.*) {
    fastcgi_cache_purge WORDPRESS "$scheme$request_method$host$1";
    }

If I comment that out, I can start up wordpress and nginx -t doesn't core
dump.

I can't see anything obvious in the release notes that would cause this,
server details are below:

Linux 3.16.0-28-generic #37-Ubuntu SMP Mon Dec 8 17:22:00 UTC 2014 i686 i686
i686 GNU/Linux

nginx version: nginx/1.7.8
TLS SNI support enabled
configure arguments: --with-cc-opt='-g -O2 -fstack-protector-strong -Wformat
-Werror=format-security -D_FORTIFY_SOURCE=2'
--with-ld-opt='-Wl,-Bsymbolic-functions -Wl,-z,relro'
--prefix=/usr/share/nginx --conf-path=/etc/nginx/nginx.conf
--http-log-path=/var/log/nginx/access.log
--error-log-path=/var/log/nginx/error.log --lock-path=/var/lock/nginx.lock
--pid-path=/run/nginx.pid --http-client-body-temp-path=/var/lib/nginx/body
--http-fastcgi-temp-path=/var/lib/nginx/fastcgi
--http-proxy-temp-path=/var/lib/nginx/proxy
--http-scgi-temp-path=/var/lib/nginx/scgi
--http-uwsgi-temp-path=/var/lib/nginx/uwsgi --with-debug --with-pcre-jit
--with-ipv6 --with-http_ssl_module --with-http_stub_status_module
--with-http_realip_module --with-http_auth_request_module
--with-http_addition_module --with-http_dav_module --with-http_flv_module
--with-http_geoip_module --with-http_gzip_static_module
--with-http_image_filter_module --with-http_mp4_module
--with-http_perl_module --with-http_random_index_module
--with-http_secure_link_module --with-http_spdy_module
--with-http_sub_module --with-http_xslt_module --with-mail
--with-mail_ssl_module
--add-module=/build/buildd/nginx-1.7.8/debian/modules/headers-more-nginx-module
--add-module=/build/buildd/nginx-1.7.8/debian/modules/nginx-auth-pam
--add-module=/build/buildd/nginx-1.7.8/debian/modules/nginx-cache-purge
--add-module=/build/buildd/nginx-1.7.8/debian/modules/nginx-dav-ext-module
--add-module=/build/buildd/nginx-1.7.8/debian/modules/nginx-development-kit
--add-module=/build/buildd/nginx-1.7.8/debian/modules/nginx-echo
--add-module=/build/buildd/nginx-1.7.8/debian/modules/ngx-fancyindex
--add-module=/build/buildd/nginx-1.7.8/debian/modules/nginx-http-push
--add-module=/build/buildd/nginx-1.7.8/debian/modules/nginx-lua
--add-module=/build/buildd/nginx-1.7.8/debian/modules/nginx-upload-progress
--add-module=/build/buildd/nginx-1.7.8/debian/modules/nginx-upstream-fair
--add-module=/build/buildd/nginx-1.7.8/debian/modules/ngx_http_substitutions_filter_module

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,255522,255522#msg-255522