[PATCH] Perl: NULL-terminate argument list

[Maxim Dounin]

Hello!

On Thu, Jun 19, 2014 at 04:17:23AM -0700, Piotr Sikora wrote:

> # HG changeset patch
> # User Piotr Sikora <piotr at cloudflare.com>
> # Date 1403176596 25200
> #      Thu Jun 19 04:16:36 2014 -0700
> # Node ID 290f3fcb9cf552c235b9807cf0af3830b5add5af
> # Parent  675bda8dcfdbf66e4a17017839f39ed6c8cbb9f5
> Perl: NULL-terminate argument list.
> 
> perl_parse() function expects argv/argc-style argument list,
> which according to the C standard must be NULL-terminated,
> that is: argv[argc] == NULL.
> 
> This change fixes a crash (SIGSEGV) that could happen because
> of the buffer overrun during perl module initialization.

The perlembed manpage is full of examples without terminating 
NULL, and it's the only documentation available for the 
perl_parse() function, AFAIK.

Could you please elaborate a bit more on the problem the patch 
tries to fix?

> 
> Signed-off-by: Piotr Sikora <piotr at cloudflare.com>
> 
> diff -r 675bda8dcfdb -r 290f3fcb9cf5 src/http/modules/perl/ngx_http_perl_module.c
> --- a/src/http/modules/perl/ngx_http_perl_module.c	Thu Jun 19 13:55:59 2014 +0400
> +++ b/src/http/modules/perl/ngx_http_perl_module.c	Thu Jun 19 04:16:36 2014 -0700
> @@ -577,7 +577,7 @@ ngx_http_perl_create_interpreter(ngx_con
>  
>      n = (pmcf->modules != NGX_CONF_UNSET_PTR) ? pmcf->modules->nelts * 2 : 0;
>  
> -    embedding = ngx_palloc(cf->pool, (4 + n) * sizeof(char *));
> +    embedding = ngx_palloc(cf->pool, (5 + n) * sizeof(char *));
>      if (embedding == NULL) {
>          goto fail;
>      }
> @@ -595,6 +595,7 @@ ngx_http_perl_create_interpreter(ngx_con
>      embedding[n++] = "-Mnginx";
>      embedding[n++] = "-e";
>      embedding[n++] = "0";
> +    embedding[n] = NULL;
>  
>      n = perl_parse(perl, ngx_http_perl_xs_init, n, embedding, NULL);

The patch itself looks fine.

-- 
Maxim Dounin
http://nginx.org/