[pkg-lxc-devel] Bug#926582: lxc-start SIGSEGV with --foreground

[Sepi Gair]

After set subgid map you should relogin or manually apply a new map to 
the current session using newgidmap. Most probably that's the cause of 
your issue. LXC does not handle such issue properly.

On Sun, 07 Apr 2019 11:21:57 +0000 itd at firemail.cc wrote:
> Package: lxc
> Version: 1:3.1.0+really3.0.3-6
> Severity: normal
> 
> Dear Maintainer,
> 
> sadly I can no longer reproduce this. It just started to work.
> Apologies for this rudimentary bug report.
> 
> > What led up to the situation?
> 
> I installed 'lxc' and configured usage of unprivileged container.
> Afterwards, I created a new unprivileged container and tried to start it 
> with:
> 
> >> $ lxc-create -t download -n debian-download -- -d debian -r buster -a 
> >> amd64
> >> $ lxc-start -n debian-download
> >> $ lxc-start -n debian-download --foreground
> 
> Command two failed, but suggested adding `--foreground`, thus I tried 
> that.
> However, command three failed with a segmentation fault.
> 
> > What exactly did you do (or not do) that was effective (or 
> > ineffective)?
> 
> Unsure how to debug this, I installed valgrind, lxc-dbgsym, and 
> liblxc1-dbgsym.
> Finally, I tried to execute:
> 
> >> $ valgrind --tool=memcheck -- lxc-start -n debian-download 
> >> --foreground
> 
> Which resulted in the following stderr/valgrind output:
> 
> ==21455== Memcheck, a memory error detector
> ==21455== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et 
> al.
> ==21455== Using Valgrind-3.14.0 and LibVEX; rerun with -h for copyright 
> info
> ==21455== Command: lxc-start -n debian-download --foreground
> ==21455==
> ==21455== Warning: noted but unhandled ioctl 0x5441 with no 
> size/direction hints.
> ==21455==    This could cause spurious value errors to appear.
> ==21455==    See README_MISSING_SYSCALL_OR_IOCTL for guidance on writing 
> a proper wrapper.
> ==21455== Invalid read of size 8
> ==21455==    at 0x4879AFD: cgfsng_payload_create (cgfsng.c:1318)
> ==21455==    by 0x48C171E: lxc_spawn (start.c:1645)
> ==21455==    by 0x48C171E: __lxc_start (start.c:1949)
> ==21455==    by 0x48C2C26: lxc_start (start.c:2065)
> ==21455==    by 0x48A9F26: do_lxcapi_start (lxccontainer.c:1096)
> ==21455==    by 0x48AA9C0: lxcapi_start (lxccontainer.c:1130)
> ==21455==    by 0x10A4EB: main (lxc_start.c:328)
> ==21455==  Address 0x0 is not stack'd, malloc'd or (recently) free'd
> ==21455==
> ==21455==
> ==21455== Process terminating with default action of signal 11 (SIGSEGV)