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Commit c7eb87c8 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Greg Kroah-Hartman
Browse files

ipc/mqueue.c: change __do_notify() to bypass check_kill_permission() 



[ Upstream commit b5f2006144c6ae941726037120fa1001ddede784 ]

Commit cc731525 ("signal: Remove kernel interal si_code magic")
changed the value of SI_FROMUSER(SI_MESGQ), this means that mq_notify() no
longer works if the sender doesn't have rights to send a signal.

Change __do_notify() to use do_send_sig_info() instead of kill_pid_info()
to avoid check_kill_permission().

This needs the additional notify.sigev_signo != 0 check, shouldn't we
change do_mq_notify() to deny sigev_signo == 0 ?

Test-case:

	#include <signal.h>
	#include <mqueue.h>
	#include <unistd.h>
	#include <sys/wait.h>
	#include <assert.h>

	static int notified;

	static void sigh(int sig)
	{
		notified = 1;
	}

	int main(void)
	{
		signal(SIGIO, sigh);

		int fd = mq_open("/mq", O_RDWR|O_CREAT, 0666, NULL);
		assert(fd >= 0);

		struct sigevent se = {
			.sigev_notify	= SIGEV_SIGNAL,
			.sigev_signo	= SIGIO,
		};
		assert(mq_notify(fd, &se) == 0);

		if (!fork()) {
			assert(setuid(1) == 0);
			mq_send(fd, "",1,0);
			return 0;
		}

		wait(NULL);
		mq_unlink("/mq");
		assert(notified);
		return 0;
	}

[manfred@colorfullife.com: 1) Add self_exec_id evaluation so that the implementation matches do_notify_parent 2) use PIDTYPE_TGID everywhere]
Fixes: cc731525 ("signal: Remove kernel interal si_code magic")
Reported-by: default avatarYoji <yoji.fujihar.min@gmail.com>
Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarManfred Spraul <manfred@colorfullife.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Acked-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Markus Elfring <elfring@users.sourceforge.net>
Cc: <1vier1@web.de>
Cc: <stable@vger.kernel.org>
Link: http://lkml.kernel.org/r/e2a782e4-eab9-4f5c-c749-c07a8f7a4e66@colorfullife.com


Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 3a3da006

ipc/mqueue.c

+26 −8
Original line number Diff line number Diff line
@@ -76,6 +76,7 @@ struct mqueue_inode_info { 


	struct sigevent notify;

	struct pid *notify_owner;

	u32 notify_self_exec_id;

	struct user_namespace *notify_user_ns;

	struct user_struct *user;	/* user who created, for accounting */

	struct sock *notify_sock;
@@ -662,28 +663,44 @@ static void __do_notify(struct mqueue_inode_info *info) 
	 * synchronously. */

	if (info->notify_owner &&

	    info->attr.mq_curmsgs == 1) {

		struct siginfo sig_i;

		switch (info->notify.sigev_notify) {

		case SIGEV_NONE:

			break;

		case SIGEV_SIGNAL:

			/* sends signal */

		case SIGEV_SIGNAL: {

			struct siginfo sig_i;

			struct task_struct *task;



			/* do_mq_notify() accepts sigev_signo == 0, why?? */

			if (!info->notify.sigev_signo)

				break;



			clear_siginfo(&sig_i);

			sig_i.si_signo = info->notify.sigev_signo;

			sig_i.si_errno = 0;

			sig_i.si_code = SI_MESGQ;

			sig_i.si_value = info->notify.sigev_value;

			/* map current pid/uid into info->owner's namespaces */

			rcu_read_lock();

			/* map current pid/uid into info->owner's namespaces */

			sig_i.si_pid = task_tgid_nr_ns(current,

						ns_of_pid(info->notify_owner));

			sig_i.si_uid = from_kuid_munged(info->notify_user_ns, current_uid());

			sig_i.si_uid = from_kuid_munged(info->notify_user_ns,

						current_uid());

			/*

			 * We can't use kill_pid_info(), this signal should

			 * bypass check_kill_permission(). It is from kernel

			 * but si_fromuser() can't know this.

			 * We do check the self_exec_id, to avoid sending

			 * signals to programs that don't expect them.

			 */

			task = pid_task(info->notify_owner, PIDTYPE_TGID);

			if (task && task->self_exec_id ==

						info->notify_self_exec_id) {

				do_send_sig_info(info->notify.sigev_signo,

						&sig_i, task, PIDTYPE_TGID);

			}

			rcu_read_unlock();



			kill_pid_info(info->notify.sigev_signo,

				      &sig_i, info->notify_owner);

			break;

		}

		case SIGEV_THREAD:

			set_cookie(info->notify_cookie, NOTIFY_WOKENUP);

			netlink_sendskb(info->notify_sock, info->notify_cookie);
@@ -1273,6 +1290,7 @@ static int do_mq_notify(mqd_t mqdes, const struct sigevent *notification) 
			info->notify.sigev_signo = notification->sigev_signo;

			info->notify.sigev_value = notification->sigev_value;

			info->notify.sigev_notify = SIGEV_SIGNAL;

			info->notify_self_exec_id = current->self_exec_id;

			break;

		}