| From foo@baz Mon Apr 9 17:09:24 CEST 2018 |
| From: Kirill Tkhai <ktkhai@virtuozzo.com> |
| Date: Mon, 8 May 2017 15:56:34 -0700 |
| Subject: pidns: disable pid allocation if pid_ns_prepare_proc() is failed in alloc_pid() |
| |
| From: Kirill Tkhai <ktkhai@virtuozzo.com> |
| |
| |
| [ Upstream commit 8896c23d2ef803f1883fea73117a435925c2b4c4 ] |
| |
| alloc_pidmap() advances pid_namespace::last_pid. When first pid |
| allocation fails, then next created process will have pid 2 and |
| pid_ns_prepare_proc() won't be called. So, pid_namespace::proc_mnt will |
| never be initialized (not to mention that there won't be a child |
| reaper). |
| |
| I saw crash stack of such case on kernel 3.10: |
| |
| BUG: unable to handle kernel NULL pointer dereference at (null) |
| IP: proc_flush_task+0x8f/0x1b0 |
| Call Trace: |
| release_task+0x3f/0x490 |
| wait_consider_task.part.10+0x7ff/0xb00 |
| do_wait+0x11f/0x280 |
| SyS_wait4+0x7d/0x110 |
| |
| We may fix this by restore of last_pid in 0 or by prohibiting of futher |
| allocations. Since there was a similar issue in Oleg Nesterov's commit |
| 314a8ad0f18a ("pidns: fix free_pid() to handle the first fork failure"). |
| and it was fixed via prohibiting allocation, let's follow this way, and |
| do the same. |
| |
| Link: http://lkml.kernel.org/r/149201021004.4863.6762095011554287922.stgit@localhost.localdomain |
| Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com> |
| Acked-by: Cyrill Gorcunov <gorcunov@openvz.org> |
| Cc: Andrei Vagin <avagin@virtuozzo.com> |
| Cc: Andreas Gruenbacher <agruenba@redhat.com> |
| Cc: Kees Cook <keescook@chromium.org> |
| Cc: Michael Kerrisk <mtk.manpages@googlemail.com> |
| Cc: Al Viro <viro@zeniv.linux.org.uk> |
| Cc: Oleg Nesterov <oleg@redhat.com> |
| Cc: Paul Moore <paul@paul-moore.com> |
| Cc: Eric Biederman <ebiederm@xmission.com> |
| Cc: Andy Lutomirski <luto@amacapital.net> |
| Cc: Ingo Molnar <mingo@kernel.org> |
| Cc: Serge Hallyn <serge@hallyn.com> |
| Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
| Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
| Signed-off-by: Sasha Levin <alexander.levin@microsoft.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| kernel/pid.c | 4 +++- |
| 1 file changed, 3 insertions(+), 1 deletion(-) |
| |
| --- a/kernel/pid.c |
| +++ b/kernel/pid.c |
| @@ -322,8 +322,10 @@ struct pid *alloc_pid(struct pid_namespa |
| } |
| |
| if (unlikely(is_child_reaper(pid))) { |
| - if (pid_ns_prepare_proc(ns)) |
| + if (pid_ns_prepare_proc(ns)) { |
| + disable_pid_allocation(ns); |
| goto out_free; |
| + } |
| } |
| |
| get_pid_ns(ns); |