Backport #1567: socket.c silently discards internal listen(2) failures

• Status: Closed
• Assignee: yugui (Yuki Sonoda)

[pilcrow (Mike Pomraning)]

=begin
Symptom:
TCPServer.new(...) may appear to succeed, even though its implied listen(2) call has silently failed. Similarly for UNIXServer.new().

Expectation:
Failures in the underlying listen(2) call should translate to the appropriate ruby SystemCallError.

Patch:
The attached patch looks to me to address the issue under 1.9.1, and test/socket/* test cases all pass with it.

Background:
ext/socket/socket.c init_inetsock_internal() and init_unixsock() each conditionally call listen(2) but discard its return value. This behavior is incorrect, possibly leaving the caller with an unlistening socket when a listening one was expected, and inconsistent with the way those init_ functions handle failures of other implied socket calls, such as bind(2) or connect(2).

It is tempting to omit error-checking listen(2) calls when the preceding, successful socket(2) and bind(2) calls are close by and visually verifiable (as in the init_* functions), since the most familiar listen(2) failures result from the programmer mistakenly operating on an inappropriate file descriptor. However, misbehaving threads can modify the file descriptor table behind our backs (EBADF), system/process failures do occur (ENOBUFS, EACCES) on some platforms, and LD_PRELOADed libraries may play wild tricks with socketry (EGOODLUCK). For these reasons, the init_ functions should rb_sys_fail when listen(2) fails.
=end

[pilcrow (Mike Pomraning)]

• File ruby-1.9.1-p129-socket_listen_2.patch ruby-1.9.1-p129-socket_listen_2.patch added

=begin
Mea culpa: the attached patch close(2)s socket fd if listen(2) fails inside TCPServer initialization.

With respect to SystemCallError behavior, one can (on Linux, at least) verify behavior like so:

$ cat /tmp/listen_fail.c
#include <errno.h>

/* gcc -fPIC -rdynamic -g -c -Wall listen_fail.c
* gcc -shared -Wl,-soname,liblisten_fail.so.1 -o liblisten_fail.so.1 listen_fail.o -lc
*/

int
listen(int s, int backlog)
{
errno = ENOBUFS;
return -1;
}

$ basename pwd
ruby-1.9.1-p129

without patch

$ LD_PRELOAD=/tmp/liblisten_fail.so.1 ./miniruby -I./lib -I.ext/common -I./- -r./ext/purelib.rb ./runruby.rb --extout=.ext -r socket -e 'TCPServer.new(1024)'
$

with patch

$ LD_PRELOAD=/tmp/liblisten_fail.so.1 ./miniruby -I./lib -I.ext/common -I./- -r./ext/purelib.rb ./runruby.rb --extout=.ext -r socket -e 'TCPServer.new(1024)'
-e:1:in initialize': No buffer space available - listen(2) (Errno::ENOBUFS) from -e:1:in new'
from -e:1:in `'

... and similarly for UNIXServer.new(...)
=end

[rogerdpack (Roger Pack)]

=begin
was this updated in trunk? if so which revision?
=end

[mame (Yusuke Endoh)]

• Assignee set to mame (Yusuke Endoh)

=begin
Hi,

Thank you for reporting. I agree that this is certainly a bug.

Unfortunately, your patch causes errors when running rubyspec
because it closes invalid fd when bind(2) fails.

The following patch would work. I'll commit soon.

diff --git a/ext/socket/ipsocket.c b/ext/socket/ipsocket.c
index 447ae40..b6b2426 100644
--- a/ext/socket/ipsocket.c
+++ b/ext/socket/ipsocket.c
@@ -104,8 +104,13 @@ init_inetsock_internal(struct inetsock_arg *arg)

  arg->fd = -1;

• if (type == INET_SERVER)
• listen(fd, 5);

• if (type == INET_SERVER) {

• status = listen(fd, 5);

• if (status < 0) {

•  close(fd);
  

•  syscall = "listen(2)";
  

• }

• }

  /* create new instance */
  return rsock_init_sock(arg->sock, fd);
  diff --git a/ext/socket/unixsocket.c b/ext/socket/unixsocket.c
  index 907f89c..4c3c5a7 100644
  --- a/ext/socket/unixsocket.c
  +++ b/ext/socket/unixsocket.c
  @@ -65,7 +65,12 @@ rsock_init_unixsock(VALUE sock, VALUE path, int server)
  rb_sys_fail(sockaddr.sun_path);
  }

• if (server) listen(fd, 5);

• if (server) {

• if (listen(fd, 5) < 0) {

•  close(fd);
  

•  rb_sys_fail("listen(2)");
  

• }

• }

  rsock_init_sock(sock, fd);
  if (server) {

--
Yusuke Endoh [e-mail]
=end

[mame (Yusuke Endoh)]

• Assignee changed from mame (Yusuke Endoh) to yugui (Yuki Sonoda)

=begin
Applied at r27272. Moved to Backport tracker.

--
Yusuke Endoh [e-mail]
=end

[shyouhei (Shyouhei Urabe)]

• Status changed from Open to Assigned

=begin

=end

[jeremyevans0 (Jeremy Evans)]

• Description updated (diff)
• Status changed from Assigned to Closed