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

From: Zhao Lei
Date: Fri Apr 15 2016 - 06:49:40 EST


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(-)

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1.8.5.1