This is a note to let you know that I've just added the patch titled
pid: fix lockdep deadlock warning due to ucount_lock
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
pid-fix-lockdep-deadlock-warning-due-to-ucount_lock.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From add7c65ca426b7a37184dd3d2172394e23d585d6 Mon Sep 17 00:00:00 2001
From: Andrei Vagin <avagin@xxxxxxxxxx>
Date: Wed, 4 Jan 2017 19:28:14 -0800
Subject: pid: fix lockdep deadlock warning due to ucount_lock
From: Andrei Vagin <avagin@xxxxxxxxxx>
commit add7c65ca426b7a37184dd3d2172394e23d585d6 upstream.
=========================================================
[ INFO: possible irq lock inversion dependency detected ]
4.10.0-rc2-00024-g4aecec9-dirty #118 Tainted: G W
---------------------------------------------------------
swapper/1/0 just changed the state of lock:
(&(&sighand->siglock)->rlock){-.....}, at: [<ffffffffbd0a1bc6>] __lock_task_sighand+0xb6/0x2c0
but this lock took another, HARDIRQ-unsafe lock in the past:
(ucounts_lock){+.+...}
and interrupts could create inverse lock ordering between them.
other info that might help us debug this:
Chain exists of: &(&sighand->siglock)->rlock --> &(&tty->ctrl_lock)->rlock --> ucounts_lock
Possible interrupt unsafe locking scenario:
CPU0 CPU1
---- ----
lock(ucounts_lock);
local_irq_disable();
lock(&(&sighand->siglock)->rlock);
lock(&(&tty->ctrl_lock)->rlock);
<Interrupt>
lock(&(&sighand->siglock)->rlock);
*** DEADLOCK ***
This patch removes a dependency between rlock and ucount_lock.
Fixes: f333c700c610 ("pidns: Add a limit on the number of pid namespaces")
Signed-off-by: Andrei Vagin <avagin@xxxxxxxxxx>
Acked-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/pid_namespace.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -151,8 +151,12 @@ out:
static void delayed_free_pidns(struct rcu_head *p)
{
- kmem_cache_free(pid_ns_cachep,
- container_of(p, struct pid_namespace, rcu));
+ struct pid_namespace *ns = container_of(p, struct pid_namespace, rcu);
+
+ dec_pid_namespaces(ns->ucounts);
+ put_user_ns(ns->user_ns);
+
+ kmem_cache_free(pid_ns_cachep, ns);
}
static void destroy_pid_namespace(struct pid_namespace *ns)
@@ -162,8 +166,6 @@ static void destroy_pid_namespace(struct
ns_free_inum(&ns->ns);
for (i = 0; i < PIDMAP_ENTRIES; i++)
kfree(ns->pidmap[i].page);
- dec_pid_namespaces(ns->ucounts);
- put_user_ns(ns->user_ns);
call_rcu(&ns->rcu, delayed_free_pidns);
}
Patches currently in stable-queue which might be from avagin@xxxxxxxxxx are
queue-4.9/pid-fix-lockdep-deadlock-warning-due-to-ucount_lock.patch
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