+ audit-use-rcu-for-task-lookup-protection.patch added to -mm tree

+ audit-use-rcu-for-task-lookup-protection.patch added to -mm tree

[akpm]

The patch titled
     audit: use rcu for task lookup protection
has been added to the -mm tree.  Its filename is
     audit-use-rcu-for-task-lookup-protection.patch

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/SubmitChecklist when testing your code ***

See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find
out what to do about this

The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/

------------------------------------------------------
Subject: audit: use rcu for task lookup protection
From: Thomas Gleixner <tglx@linutronix.de>

Protect the task lookups in audit_receive_msg() with rcu_read_lock()
instead of tasklist_lock and use lock/unlock_sighand to protect against
the exit race.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric Paris <eparis@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 kernel/audit.c |   30 ++++++++++++++----------------
 1 file changed, 14 insertions(+), 16 deletions(-)

diff -puN kernel/audit.c~audit-use-rcu-for-task-lookup-protection kernel/audit.c
--- a/kernel/audit.c~audit-use-rcu-for-task-lookup-protection
+++ a/kernel/audit.c
@@ -873,17 +873,16 @@ static int audit_receive_msg(struct sk_b
 	case AUDIT_TTY_GET: {
 		struct audit_tty_status s;
 		struct task_struct *tsk;
+		unsigned long flags;
 
-		read_lock(&tasklist_lock);
+		rcu_read_lock();
 		tsk = find_task_by_vpid(pid);
-		if (!tsk)
-			err = -ESRCH;
-		else {
-			spin_lock_irq(&tsk->sighand->siglock);
+		if (tsk && lock_task_sighand(tsk, &flags)) {
 			s.enabled = tsk->signal->audit_tty != 0;
-			spin_unlock_irq(&tsk->sighand->siglock);
-		}
-		read_unlock(&tasklist_lock);
+			unlock_task_sighand(tsk, &flags);
+		} else
+			err = -ESRCH;
+		rcu_read_unlock();
 
 		if (!err)
 			audit_send_reply(NETLINK_CB(skb).pid, seq,
@@ -893,22 +892,21 @@ static int audit_receive_msg(struct sk_b
 	case AUDIT_TTY_SET: {
 		struct audit_tty_status *s;
 		struct task_struct *tsk;
+		unsigned long flags;
 
 		if (nlh->nlmsg_len < sizeof(struct audit_tty_status))
 			return -EINVAL;
 		s = data;
 		if (s->enabled != 0 && s->enabled != 1)
 			return -EINVAL;
-		read_lock(&tasklist_lock);
+		rcu_read_lock();
 		tsk = find_task_by_vpid(pid);
-		if (!tsk)
-			err = -ESRCH;
-		else {
-			spin_lock_irq(&tsk->sighand->siglock);
+		if (tsk && lock_task_sighand(tsk, &flags)) {
 			tsk->signal->audit_tty = s->enabled != 0;
-			spin_unlock_irq(&tsk->sighand->siglock);
-		}
-		read_unlock(&tasklist_lock);
+			unlock_task_sighand(tsk, &flags);
+		} else
+			err = -ESRCH;
+		rcu_read_unlock();
 		break;
 	}
 	default:
_

Patches currently in -mm which might be from tglx@linutronix.de are

linux-next.patch
audit-call-tty_audit_push_task-outside-preempt-disabled.patch
audit-do-not-send-uninitialized-data-for-audit_tty_get.patch
audit-use-rcu-for-task-lookup-protection.patch
time-compensate-for-rounding-on-odd-frequency-clocksources.patch
x86-enable-arch_dma_addr_t_64bit-with-x86_64-highmem64g.patch
hpet-fix-unwanted-interrupt-due-to-stale-irq-status-bit.patch
hpet-factor-timer-allocate-from-open.patch
timer_list-remove-alignment-padding-on-64-bit-when-config_timer_stats.patch
timer-initialize-the-field-slack-of-timer_list.patch
kernel-time-use-array_size-macro-in-timecomparec.patch
sched-make-sched_param-argument-static-variables-in-some-sched_setscheduler-caller.patch
kernelh-add-minmax3-macros.patch
kernelh-add-minmax3-macros-fix.patch
replace-nested-max-min-macros-with-maxmin3-macro.patch
add-the-common-dma_addr_t-typedef-to-include-linux-typesh.patch
select-rename-estimate_accuracy-to-select_estimate_accuracy.patch
epoll-make-epoll_wait-use-the-hrtimer-range-feature.patch