From: Oleg Nesterov <oleg@redhat.com>
Date: Sun, 26 Aug 2012 19:12:14 +0000 (+0200)
Subject: task_work: Revert "hold task_lock around checks in keyctl"
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=b3f68f16dbcde6fcdf0fd27695391ff7e9d41233;p=GitHub%2FLineageOS%2Fandroid_kernel_samsung_universal7580.git

task_work: Revert "hold task_lock around checks in keyctl"

This reverts commit d35abdb28824cf74f0a106a0f9c6f3ff700a35bf.

task_lock() was added to ensure exit_mm() and thus exit_task_work() is
not possible before task_work_add().

This is wrong, task_lock() must not be nested with write_lock(tasklist).
And this is no longer needed, task_work_add() now fails if it is called
after exit_task_work().

Reported-by: Dave Jones <davej@redhat.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/20120826191214.GA4231@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---

diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index 3364fbf4680..6cfc6478863 100644
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -1486,7 +1486,6 @@ long keyctl_session_to_parent(void)
 	oldwork = NULL;
 	parent = me->real_parent;
 
-	task_lock(parent);
 	/* the parent mustn't be init and mustn't be a kernel thread */
 	if (parent->pid <= 1 || !parent->mm)
 		goto unlock;
@@ -1530,7 +1529,6 @@ long keyctl_session_to_parent(void)
 	if (!ret)
 		newwork = NULL;
 unlock:
-	task_unlock(parent);
 	write_unlock_irq(&tasklist_lock);
 	rcu_read_unlock();
 	if (oldwork)