Segfault in perl module's r->print

[Maxim Dounin]

Hello!

On Sun, Apr 24, 2011 at 06:50:07AM -0400, Rob wrote:

> Using $r->print() in nginx1.0's perl module leads to a segfault. The
> problem appears to be in nginx-land, not perl land.
> I am using the first example listed on
> http://wiki.nginx.org/EmbeddedPerlModule - this example works fine if
> the $r->print()'s are commented out.
> 
> Being unfamiliar with the code, I've been unable to find where
> ngx_pcalloc() is being called from XS_nginx_print (in
> modules/perl/nginx.xs),
> this seems like it'd be a fairly simple problem to fix but being
> unfamiliar with the code I've been unable to track it down - so far.
> Any assistance would be much appreciated.
> 
> backtrace:
> #0  0x00007ff6c3421686 in memset () from /lib/libc.so.6
> #1  0x000000000040f437 in ngx_pcalloc (pool=0xbc4210, size=80) at
> src/core/ngx_palloc.c:306
> #2  0x00007ff6c2f63647 in XS_nginx_print (my_perl=0xb39b20, cv=<value
> optimized out>) at nginx.xs:543
> #3  0x00007ff6c3e5ec0f in Perl_pp_entersub () from /usr/lib/libperl.so.5.10
> #4  0x00007ff6c3e5cf86 in Perl_runops_standard () from /usr/lib/libperl.so.5.10
> #5  0x00007ff6c3e5a9ed in Perl_call_sv () from /usr/lib/libperl.so.5.10
> #6  0x0000000000478548 in ngx_http_perl_call_handler
> (my_perl=0xb39b20, r=0xbc3cf0, nginx=0xb5d7f8, sub=0xb5dbb8, args=0x0,
> handler=0xb3cfa0, rv=0x0)
>     at src/http/modules/perl/ngx_http_perl_module.c:703
> #7  0x00000000004778a6 in ngx_http_perl_handle_request (r=0xbc3cf0) at
> src/http/modules/perl/ngx_http_perl_module.c:221
> 
> 
> Build details:
> CFLAGS="-g3" ./configure --prefix=/home/coder/nginx/install/
> --without-http-cache --without-http_charset_module
> --without-http_ssi_module --without-http_userid_module
> --without-http_auth_basic_module --without-http_autoindex_module
> --without-http_geo_module --without-http_split_clients_module
> --without-http_proxy_module --without-http_fastcgi_module
> --without-http_uwsgi_module --without-http_scgi_module
> --without-http_memcached_module --without-http_empty_gif_module
> --without-http_browser_module --without-http_upstream_ip_hash_module
> --with-file-aio --with-libatomic --with-http_dav_module
> --with-http_perl_module
> 
> gcc version 4.4.1 (Ubuntu 4.4.1-4ubuntu9)
> perl v5.10.0

Works ok here.

Most likely you have your nginx perl module (nginx.so) and nginx 
itself are out of sync, i.e. compiled with different configure 
options.  This way I may reproduce similar segfault.

At least "--without-http-cache" will result in ABI change 
(compared to nginx compiled with cache), so there is no surprise 
it segfaults as a result.

Maxim Dounin