RE: [PATCH 0/3] Write dump into container's filesystem for pipe_type core_pattern

[Zhao Lei]

(Offline)

Hi, Eric

I rewrited patch to support code_dump in container according to
your suggestion.

Could you take a look of it, and give me your opinion in this version?

Thanks
Zhaolei

> -----Original Message-----
> From: Zhao Lei [mailto:zhaolei@xxxxxxxxxxxxxx]
> Sent: Wednesday, May 11, 2016 9:27 AM
> To: linux-kernel@xxxxxxxxxxxxxxx
> Cc: containers@xxxxxxxxxxxxxxxxxxxxxxxxxx; Eric W. Biederman
> <ebiederm@xxxxxxxxxxxx>; Mateusz Guzik <mguzik@xxxxxxxxxx>;
> Kamezawa Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>; Zhao Lei
> <zhaolei@xxxxxxxxxxxxxx>
> Subject: [PATCH 0/3] Write dump into container's filesystem for pipe_type
> core_pattern
> 
> In current system, when we set core_pattern to a pipe, both pipe program
> and program's output are in host's filesystem.
> But when we set core_pattern to a file, the container will write dump
> into container's filesystem.
> 
> For example, when we set following core_pattern:
>  # echo "|/my_dump_pipe %s %c %p %u %g %t
> e" >/proc/sys/kernel/core_pattern
> and trigger a segment fault in a container, my_dump_pipe is searched from
> host's filesystem, and it will write coredump into host's filesystem too.
> 
> In a privileged container, user can destroy host system by following
> command:
>  # # In a container
>  # echo "|/bin/dd of=/boot/vmlinuz" >/proc/sys/kernel/core_pattern
>  # make_dump
> 
> Actually, all operation in a container should not change host's
> environment, the container should use core_pattern as its private setting.
> In detail, in core dump action:
> 1: Search pipe program in container's fs namespace.
> 2: Run pipe program in container's fs namespace to write coredump to it.
> 
> I rewrited this patch from origional:
> 
> http://www.gossamer-threads.com/lists/linux/kernel/2395715?do=post_view_
> flat
> and changed the impliment way and function detail discussed in:
> 
> http://www.gossamer-threads.com/lists/linux/kernel/2397602?nohighlight=1#
> 2397602
> 
> Changes against previous impliment:
> 1: Avoid forking thread from the crach process.
>    Suggested-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
> 2: To keep compatibility with current code, if user hadn't change
>    core_pattern in container, the dump file will still write to
>    the host filesystem.
>    Suggested-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
> 
> Zhao Lei (3):
>   [RFC] Save dump_root into pid_namespace
>   [RFC] Make dump_pipe thread possilbe to select the rootfs
>   [RFC] Write dump into container's filesystem for pipe_type
>     core_pattern
> 
>  fs/coredump.c                 | 19 ++++++++++++++++++-
>  fs/fs_struct.c                | 25 ++++++++++++++++---------
>  include/linux/fs_struct.h     |  3 ++-
>  include/linux/kmod.h          |  4 +++-
>  include/linux/pid_namespace.h |  3 +++
>  include/linux/sched.h         |  5 +++--
>  init/do_mounts_initrd.c       |  3 ++-
>  init/main.c                   |  4 ++--
>  kernel/fork.c                 | 34 ++++++++++++++++++++--------------
>  kernel/kmod.c                 | 13 ++++++++-----
>  kernel/kthread.c              |  3 ++-
>  kernel/pid.c                  |  1 +
>  kernel/pid_namespace.c        |  6 ++++++
>  kernel/sysctl.c               | 30 ++++++++++++++++++++++++++----
>  lib/kobject_uevent.c          |  3 ++-
>  security/keys/request_key.c   |  2 +-
>  16 files changed, 115 insertions(+), 43 deletions(-)
> 
> --
> 1.8.5.1