Segmentation fault

[yyamano]

I get seg fault with the following configuration and client code while writing code to reproduce another problem. The bug is not high priority to me for now.

        location /FOO {
          mruby_enable_read_request_body on;
          mruby_set_code $body '
            Nginx.log Nginx::LOG_ERR, "reading body..."
            req = Nginx::Request.new
            begin
              rc = req.read_body
              body = req.get_body
              Nginx.log Nginx::LOG_ERR, "path=#{req.uri}, method=#{req.method}, rc=#{rc}, body=#{body}"
            rescue => e
              Nginx.log Nginx::LOG_ERR, "Failed to read a request body: #{e.class}: #{e.message}"
            end
            body
          ';
          mruby_content_handler_code '
            begin
              body = Nginx::Request.new.var.body
              raise "body is nil or empty" if body.nil? || body.empty?
              Nginx.rputs body
            rescue => e
              Nginx.log Nginx::LOG_ERR, "Failed to get a request body: #{e.class}: #{e.message}"
              Nginx.rputs "Failed to get a request body"
            end
          ';
        }

#!/usr/bin/env ruby

require 'socket'

request_body = %({"hello": "ngx_mruby"})
headers = <<HEAD.gsub("\n", "\r\n")
POST /FOO HTTP/1.0
Content-Type: application/json
User-Agent: issue-268-test
Content-Length: #{request_body.length}
HEAD

Socket.tcp("localhost", 58080) do |s|
  s.print headers
  s.print "\r\n"
  sleep 0.3 # <==== important!
  s.print request_body
  s.close_write
  puts s.read
end

Here is a gdb backtrace.

Program received signal SIGSEGV, Segmentation fault.
0x00000000005512ab in ngx_mrb_rputs_inner (mrb=0xbe6da0, self=..., with_lf=0)
    at /home/vagrant/ngx_mruby/src/http/ngx_http_mruby_core.c:114
114	  if (ctx->rputs_chain == NULL) {
Missing separate debuginfos, use: debuginfo-install glibc-2.17-106.el7_2.6.x86_64 nss-softokn-freebl-3.16.2.3-13.el7_1.x86_64 openssl-libs-1.0.1e-51.el7_2.5.x86_64 pcre-8.32-15.el7_2.1.x86_64 zlib-1.2.7-15.el7.x86_64
(gdb) bt
#0  0x00000000005512ab in ngx_mrb_rputs_inner (mrb=0xbe6da0, self=..., with_lf=0)
    at /home/vagrant/ngx_mruby/src/http/ngx_http_mruby_core.c:114
#1  0x00000000005515a1 in ngx_mrb_rputs (mrb=0xbe6da0, self=...) at /home/vagrant/ngx_mruby/src/http/ngx_http_mruby_core.c:161
#2  0x0000000000581099 in mrb_vm_exec (mrb=mrb@entry=0xbe6da0, proc=0xc35880, pc=0xd1dc90)
    at /home/vagrant/ngx_mruby/mruby/src/vm.c:1265
#3  0x00000000005873b1 in mrb_vm_run (stack_keep=<optimized out>, self=..., proc=<optimized out>, mrb=0xbe6da0)
    at /home/vagrant/ngx_mruby/mruby/src/vm.c:821
#4  mrb_run (mrb=0xbe6da0, proc=<optimized out>, self=...) at /home/vagrant/ngx_mruby/mruby/src/vm.c:2617
#5  0x000000000054c61a in ngx_mrb_run (r=0xbe3bb0, state=0xbe00d0, code=0xd26450, cached=1, result=0x0)
    at /home/vagrant/ngx_mruby/src/http/ngx_http_mruby_module.c:820
#6  0x000000000054ed25 in ngx_http_mruby_content_inline_handler (r=0xbe3bb0)
    at /home/vagrant/ngx_mruby/src/http/ngx_http_mruby_module.c:1530
#7  0x00000000004aefd5 in ngx_http_core_content_phase (r=0xbe3bb0, ph=0xd34150) at src/http/ngx_http_core_module.c:1393
#8  0x00000000004ada3f in ngx_http_core_run_phases (r=0xbe3bb0) at src/http/ngx_http_core_module.c:860
#9  0x00000000004ad9ad in ngx_http_handler (r=0xbe3bb0) at src/http/ngx_http_core_module.c:843
#10 0x00000000004bd6de in ngx_http_process_request (r=0xbe3bb0) at src/http/ngx_http_request.c:1921
#11 0x00000000004bc067 in ngx_http_process_request_headers (rev=0xbd3a30) at src/http/ngx_http_request.c:1348
#12 0x00000000004bb44a in ngx_http_process_request_line (rev=0xbd3a30) at src/http/ngx_http_request.c:1028
#13 0x00000000004ba0a1 in ngx_http_wait_request_handler (rev=0xbd3a30) at src/http/ngx_http_request.c:503
#14 0x000000000049cad3 in ngx_epoll_process_events (cycle=0xbcf530, timer=60000, flags=1)
    at src/event/modules/ngx_epoll_module.c:902
#15 0x000000000048bb0d in ngx_process_events_and_timers (cycle=0xbcf530) at src/event/ngx_event.c:242
#16 0x0000000000498f95 in ngx_single_process_cycle (cycle=0xbcf530) at src/os/unix/ngx_process_cycle.c:309
#17 0x0000000000457a6b in main (argc=1, argv=0x7fffffffe408) at src/core/nginx.c:372
(gdb) p ctx
$1 = (ngx_http_mruby_ctx_t *) 0x0

[yyamano]

I can't reproduce the problem with the latest version of ngx_mruby.
See https://github.com/yyamano/ngx_mruby/tree/issue-282

[matsumotory]

Thanks always!