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To: FreeBSD-gnats-submit@freebsd.org
Subject: Truss segfaults when tracing sshd
From: Anders Nordby <anders@FreeBSD.org>
Reply-To: Anders Nordby <anders@FreeBSD.org>
Cc: current@FreeBSD.org
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>Submitter-Id:	current-users
>Originator:	Anders Nordby <anders@FreeBSD.org>
>Organization:	
>Confidential:	no 
>Synopsis:	Truss segfaults when tracing sshd
>Severity:	serious
>Priority:	medium
>Category:	bin
>Class:		sw-bug
>Release:	FreeBSD 5.0-CURRENT i386
>Environment:

FreeBSD current 5.0-CURRENT FreeBSD 5.0-CURRENT #0: Sat Aug 31 09:31:05 GMT 2002     root@current:/usr/obj/usr/src/sys/MYGENERIC  i386

Filesystems mounted:

/dev/ad0s1a on / (ufs, local)
devfs on /dev (devfs, local)
/dev/ad0s1f on /tmp (ufs, local, soft-updates)
/dev/ad0s1g on /usr (ufs, local, soft-updates)
/dev/ad0s1e on /var (ufs, local, soft-updates)
eggsilo:/space/distfiles on /usr/ports/distfiles (nfs)
procfs on /proc (procfs, local)

The processor on the system is a 466 MHz Intel Celeron.

>Description:

Find your sshd process:

# sockstat -l | grep sshd
root     sshd       175   3  tcp6   *:22                  *:*
root     sshd       175   4  tcp4   *:22                  *:*

Truss it through gdb:

# gdb truss
GNU gdb 5.2.0 (FreeBSD) 20020627
Copyright 2002 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "i386-undermydesk-freebsd"...
(no debugging symbols found)...
(gdb) run -p 175
Starting program: /usr/bin/truss -p 175

Now log in to the machine (I'm logging in as root), and return to gdb:

(no debugging symbols found)...(no debugging symbols found)...
Program received signal SIGSEGV, Segmentation fault.
0x08049c77 in free ()
(gdb) bt
#0  0x08049c77 in free ()
#1  0x2806d000 in ?? ()
#2  0x08049e3e in free ()
#3  0x0804eb6d in free ()
#4  0x08049182 in free ()
#5  0x08048d31 in free ()
(gdb)

>How-To-Repeat:

On a vanilla -current system from today:

# truss -p `sockstat -l | egrep 'sshd.*tcp4' | awk '{print $3}'`

Log into the system with sshd, and truss will segfault:

Segmentation fault (core dumped)

This also seems to happen if you truss sshd while logging out another ssh
session.

>Fix:

N/A

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