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Commit 7cf7db8d authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

signals: Fix more rcu assumptions 



1) Remove the misleading comment in __sigqueue_alloc() which claims
   that holding a spinlock is equivalent to rcu_read_lock().

2) Add a rcu_read_lock/unlock around the __task_cred() access
   in __sigqueue_alloc()

This needs to be revisited to remove the remaining users of
read_lock(&tasklist_lock) but that's outside the scope of this patch.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
LKML-Reference: <20091210004703.269843657@linutronix.de>
parent 14d8c9f3

kernel/signal.c

+4 −4
Original line number Diff line number Diff line
@@ -218,13 +218,13 @@ __sigqueue_alloc(int sig, struct task_struct *t, gfp_t flags, int override_rlimi 
	struct user_struct *user;



	/*

	 * We won't get problems with the target's UID changing under us

	 * because changing it requires RCU be used, and if t != current, the

	 * caller must be holding the RCU readlock (by way of a spinlock) and

	 * we use RCU protection here

	 * Protect access to @t credentials. This can go away when all

	 * callers hold rcu read lock.

	 */

	rcu_read_lock();

	user = get_uid(__task_cred(t)->user);

	atomic_inc(&user->sigpending);

	rcu_read_unlock();



	if (override_rlimit ||

	    atomic_read(&user->sigpending) <=