Commit 02169155 authored by Eric W. Biederman's avatar Eric W. Biederman
Browse files

exec: Factor unshare_sighand out of de_thread and call it separately 



This makes the code clearer and makes it easier to implement a mutex
that is not taken over any locations that may block indefinitely waiting
for userspace.

Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
Reviewed-by: default avatarBernd Edlinger <bernd.edlinger@hotmail.de>
Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Acked-by: default avatarChristian Brauner <christian.brauner@ubuntu.com>
Reviewed-by: default avatarKirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: default avatarBernd Edlinger <bernd.edlinger@hotmail.de>
Signed-off-by: default avatarEric W. Biederman <ebiederm@xmission.com>
parent 2ca7be7d

fs/exec.c

+26 −13
Original line number Diff line number Diff line
@@ -1194,6 +1194,23 @@ no_thread_group: 
	flush_itimer_signals();

#endif



	BUG_ON(!thread_group_leader(tsk));

	return 0;



killed:

	/* protects against exit_notify() and __exit_signal() */

	read_lock(&tasklist_lock);

	sig->group_exit_task = NULL;

	sig->notify_count = 0;

	read_unlock(&tasklist_lock);

	return -EAGAIN;

}





static int unshare_sighand(struct task_struct *me)

{

	struct sighand_struct *oldsighand = me->sighand;



	if (refcount_read(&oldsighand->count) != 1) {

		struct sighand_struct *newsighand;

		/*
@@ -1210,23 +1227,13 @@ no_thread_group: 


		write_lock_irq(&tasklist_lock);

		spin_lock(&oldsighand->siglock);

		rcu_assign_pointer(tsk->sighand, newsighand);

		rcu_assign_pointer(me->sighand, newsighand);

		spin_unlock(&oldsighand->siglock);

		write_unlock_irq(&tasklist_lock);



		__cleanup_sighand(oldsighand);

	}



	BUG_ON(!thread_group_leader(tsk));

	return 0;



killed:

	/* protects against exit_notify() and __exit_signal() */

	read_lock(&tasklist_lock);

	sig->group_exit_task = NULL;

	sig->notify_count = 0;

	read_unlock(&tasklist_lock);

	return -EAGAIN;

}



char *__get_task_comm(char *buf, size_t buf_size, struct task_struct *tsk)
@@ -1264,13 +1271,19 @@ int flush_old_exec(struct linux_binprm * bprm) 
	int retval;



	/*

	 * Make sure we have a private signal table and that

	 * we are unassociated from the previous thread group.

	 * Make this the only thread in the thread group.

	 */

	retval = de_thread(me);

	if (retval)

		goto out;



	/*

	 * Make the signal table private.

	 */

	retval = unshare_sighand(me);

	if (retval)

		goto out;



	/*

	 * Must be called _before_ exec_mmap() as bprm->mm is

	 * not visibile until then. This also enables the update

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