[Buildd-tools-devel] Bug#512350: Bug#512350: schroot Segfaults When Run From eesh

[Roger Leigh]

On Mon, Jan 19, 2009 at 05:44:52PM -0500, Jacob Sherwood wrote:
> Package: schroot
> Version: 1.2.1-1
> Severity: important
> 
> schroot segfaults whenever invoked from eesh:
> 
> [Mon 12:49][pts/5 0]$ eesh exec "schroot -p echo foo bar"
> 
> And in /var/log/syslog I see:
> Jan 19 17:39:40 wolf kernel: [195438.971879] schroot[2338]: segfault at
> 0 ip 7fd0db117050 sp 7fffe4ab46c8 error 4 in
> libc-2.7.so[7fd0db09c000+14a000]
> 
> (eesh is e16's (formerly enlightenment) extended shell, if that helps at
> all).

Interesting!  I haven't seen a segfault in schroot for several years
now!

Could you possibly try running schroot in a debugger for me to
pinpoint where this occurs?  Also, the most likely cause (I think)
would be something odd being set in the environment, since that's
really the only think the shell can mess up, unless it doesn't
open stdin/stdout/stderr as expected.

Could you first, try:

Running with the additional option '--debug=notice' which will turn
on debugging output.  This will show approximately where the bug
is occuring, as well as listing the environment and the other
things schroot is doing when starting up.

Next, try to get the environment from /proc/pid/environ for the
schroot process.  If it segfaults too quickly to do this, you
can run in gdb and do "break read" (for example) to stop it ASAP.
Also see next paragraph for using gdb.

Also, the environment in eesh (I guess just type "set") should be
the same, so this would also be useful information.

Next, if you have the time, you could try running in a debugger to
pointpoint the exact place where it fails.  This will require building
a version of schroot with debugging symbols:

apt-get source schroot
cd schroot-xxx
DEB_BUILD_OPTIONS=nostrip dpkg-buildpackage -us -uc
dpkg -i schroot-xxx.deb (plus the other packages if needed)
Also make sure these packages are installed: 
libc6-dbg libstdc++6-xx-dbg (xx=GCC version) libboostxx-dbg (xx=boost version)
Next, run schroot but from eesh and in gdb:

gdb /usr/bin/schroot
run [args]
[program will run and then segfault]
backtrace
[gdb will print a stack trace which should show the point of
 failure and the calls which let up to this]

If you can find time to do this additional investigation, it will make
fixing this much faster, and would be greatly appreciated.


Many thanks,
Roger

-- 
  .''`.  Roger Leigh
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