Aurelien,
I doubt "linuxthreads" is anything but an old directory being reused.
The file gai_misc.h appears in two places. The one I mention below in
the debian and another in the ./resolve directory. The debian tree
version appears to be someone's attempt at optimizing memory usage on
the secondary thread. The debian version overrides the libc/resolve
version. The secondary thread is created by a conventional pthreads
call (again unrelated to "linuxthreads").
The reduced stack size is now being pounded by what appears to be a
ton of relatively new getaddrinfo code. __res_vinit() has a large
buffer it takes out of the stack. It makes sense that the stack is
now to small.
I ask that you give the bug serious consideration as written. I
followed this through from several angles: register analysis, note of
mmap/mprotect commands in strace, gdb si stepping, and finally code
changes with unit tests.
Thanks,
Matthew
On Aug 13, 2008, at 7:38 PM, Aurelien Jarno wrote:
On Wed, Aug 13, 2008 at 02:53:44PM -0400, Matthew Von-Maszewski wrote:
Package: libc6
Version: 2.7-13
Severity: important
Tags: patch
getaddrinfo_a creates a segfault in its worker thread due to the
stack
size being too small. Segfault happens here:
Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x40003950 (LWP 25753)]
__res_vinit (statp=0x40003dc8, preinit=0) at res_init.c:179
179 statp->id = res_randomid();
Upon entering __res_vinit, the stack pointer goes into the 0x1000
byte
guard region at the bottom of the thread's segment.
The call into res_randomid causes the segment violation. The code in
res_randomid is never reached.
Here is a sample program to tickle the bug:
#include <string.h>
#include <netdb.h>
#include <signal.h>
int
main(void)
{
int ret_val;
struct sigevent sig;
struct gaicb gaistruct;
memset(&gaistruct, 0, sizeof(gaistruct));
struct gaicb *gptr[1];
gptr[0] = &gaistruct;
memset(&sig, 0, sizeof(sig));
gptr[0]->ar_name = "a";
sig.sigev_notify = SIGEV_NONE;
ret_val = getaddrinfo_a(GAI_WAIT, gptr, 1, &sig);
return 0;
}
Root cause of the bug is in debian/linuxthreads/sysdeps/pthread/
gai_misc.h. The code sets the stack size for
Are you kidding? linuxthreads is not used on amd64 for a long time.
Given
this code is not even compiled on amd64, it can't be the root of the
problem.
--
.''`. Aurelien Jarno | GPG: 1024D/F1BCDB73
: :' : Debian developer | Electrical Engineer
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