Lua VM crash when using ngx.exec(), unsafe uri

See crash point: ngx_http_lua_control.c.

this code return NGX_HTTP_INTERNAL_SERVER_ERROR; causes the VM to crash.

detail:

• version openresty-1.9.7.3 and ngx_lua-0.10.0
• system log

Oct 28 15:11:18 f02 kernel: nginx[14476]: segfault at 140d92420 ip 00007fe7f20ee40d sp 00007fff66396f20 error 4 in libluajit-5.1.so.2[7fe7f20e5000+c1000]
Oct 28 15:11:39 f02 kernel: nginx[14489]: segfault at 141380a48 ip 00007fe7f20ee40d sp 00007fff66396ea0 error 4 in libluajit-5.1.so.2[7fe7f20e5000+c1000]
Oct 28 15:11:59 f02 kernel: nginx[14486]: segfault at 141eb8f10 ip 00007fe7f20ee40d sp 00007fff66396ea0 error 4 in libluajit-5.1.so.2[7fe7f20e5000+c1000]

• nginx log

2016/11/02 17:24:22 [error] 21115#0: *60 unsafe URI "/error_page/../" was detected *******

• configure

        location / {
            content_by_lua_block {
                ngx.log(ngx.ERR, "/error_page/ ")
                return ngx.exec("/error_page/../")
            }
        }

• test command

wget http://localhost/ -SO/dev/null

Start with src/ngx_http_lua_control.c at lines 110-112 and reproduce the report using the shown location block, unsafe URI, and wget command. Review the nginx and system logs while tracing the ngx.exec() path. Done means the unsafe URI request no longer crashes the Lua VM or nginx.