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

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[ Upstream commit b5f2006144c6ae941726037120fa1001ddede784 ]

Commit cc731525f2 ("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: cc731525f2 ("signal: Remove kernel interal si_code magic")
Reported-by: Yoji <yoji.fujihar.min@gmail.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: "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: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Oleg Nesterov 2020-05-07 18:35:39 -07:00 committed by Greg Kroah-Hartman
parent 3a3da00667
commit c7eb87c8ba
1 changed files with 26 additions and 8 deletions
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34
ipc/mqueue.c
View file

@ -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;
}