getaddrinfo_a stack overflow on 64bit - hardy

[Patrick McManus]

/home/mcmanus/t/t>lsb_release -rd
Description: Ubuntu 8.04.1
Release: 8.04

/home/mcmanus/t/t>apt-cache policy libc6
libc6:
  Installed: 2.7-10ubuntu3
  Candidate: 2.7-10ubuntu3
  Version table:
 *** 2.7-10ubuntu3 0
        500 http://us.archive.ubuntu.com hardy/main Packages
        100 /var/lib/dpkg/status

--

I think this is an upstream bug.

This sample program crashes due to a stack overflow on a thread spawned by glibc. I am not sure if that is also true on 32bit.
 (Complile as gcc poc.c -lresolv -ldl -lpthread -lanl )

#define _GNU_SOURCE
#include <netdb.h>
#include <string.h>

main()
{
    struct gaicb gb, *list[1];
    struct addrinfo hints;

    memset (&hints, 0 , sizeof (hints));
    list[0] = &gb;
    memset (&gb, 0, sizeof (gb));
    gb.ar_name = "www.ducksong.com";
    gb.ar_service = NULL;
    gb.ar_request = &hints;
    gb.ar_result = NULL;
    getaddrinfo_a (GAI_WAIT, list, 1, NULL);

    return 0;
}

In addition to the SEGV, valgrind reports
==21077==
==21077== Process terminating with default action of signal 11 (SIGSEGV)
==21077== Bad permissions for mapped region at address 0x4023A88
==21077== at 0x57477CC: __res_vinit (res_init.c:571)
==21077== by 0x7FF0005FF: ???
==21077== by 0x802BF: ???

The following patch to libc lets the program run without error and gets valgrind a clean bill of health.

diff -ur glibc-2.7/nptl/sysdeps/pthread/gai_misc.h ../../glibc-2.7/nptl/sysdeps/pthread/gai_misc.h
--- glibc-2.7/nptl/sysdeps/pthread/gai_misc.h 2007-07-28 15:30:21.000000000 -0400
+++ ../../glibc-2.7/nptl/sysdeps/pthread/gai_misc.h 2008-09-09 11:02:59.293997492 -0400
@@ -97,7 +97,7 @@
   pthread_attr_setdetachstate (&attr, PTHREAD_CREATE_DETACHED);

   /* The helper thread needs only very little resources. */
- (void) pthread_attr_setstacksize (&attr, PTHREAD_STACK_MIN);
+ (void) pthread_attr_setstacksize (&attr, 24*1024);

   /* Block all signals in the helper thread. To do this thoroughly we
      temporarily have to block all signals here. */

[Aurelien Jarno (aurelien-aurel32)]

The following code segfaults with at least glibc >= 2.7 (and CVS). It works
correctly with versions 2.3.X. I have tested versions in between.

#define _GNU_SOURCE

#include <string.h>
#include <netdb.h>
#include <signal.h>
#include <stdio.h>

int
main (void)
{
#define N 10
  struct gaicb reqmem[N];
  struct gaicb *req[N];
  int n;

  for (n = 0; n < N; ++n)
    {
      asprintf (&reqmem[n].ar_name, "test%d.test.redhat.com", 140 + n);
      reqmem[n].ar_service = NULL;
      reqmem[n].ar_request = NULL;
      reqmem[n].ar_result = NULL;
      req[n] = &reqmem[n];
    }

  getaddrinfo_a (GAI_NOWAIT, req, N, NULL);

  return 0;
}

[Drepper-fsp (drepper-fsp)]

Fixed in cvs.