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authorKirill Tkhai <ktkhai@virtuozzo.com>2017-05-08 15:56:34 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-04-13 19:47:53 +0200
commita2095be2ad9106ad92cfb906088ffc5831f0e74c (patch)
treee90bdb346f28b2be9c93bece2aec3253528bac8e /kernel
parenta90e9ee704b291125d0dda967e14a3340567afab (diff)
pidns: disable pid allocation if pid_ns_prepare_proc() is failed in alloc_pid()
[ 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>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/pid.c4
1 files changed, 3 insertions, 1 deletions
diff --git a/kernel/pid.c b/kernel/pid.c
index 693a64385d59..fa704f88ff8e 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -322,8 +322,10 @@ struct pid *alloc_pid(struct pid_namespace *ns)
}
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);