From: Oleg Nesterov <oleg@xxxxxxxxxx>
Subject: ipc/mqueue.c: change __do_notify() to bypass check_kill_permission()
Commit cc731525f26a ("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@xxxxxxxxxxxxxxxx: 1) Add self_exec_id evaluation so that the implementation matches do_notify_parent 2) use PIDTYPE_TGID everywhere]
Link: http://lkml.kernel.org/r/e2a782e4-eab9-4f5c-c749-c07a8f7a4e66@xxxxxxxxxxxxxxxx
Fixes: cc731525f26a ("signal: Remove kernel interal si_code magic")
Reported-by: Yoji <yoji.fujihar.min@xxxxxxxxx>
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Signed-off-by: Manfred Spraul <manfred@xxxxxxxxxxxxxxxx>
Acked-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Cc: Markus Elfring <elfring@xxxxxxxxxxxxxxxxxxxxx>
Cc: <1vier1@xxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
ipc/mqueue.c | 34 ++++++++++++++++++++++++++--------
1 file changed, 26 insertions(+), 8 deletions(-)
--- a/ipc/mqueue.c~ipc-mqueuec-change-__do_notify-to-bypass-check_kill_permission-v2
+++ a/ipc/mqueue.c
@@ -142,6 +142,7 @@ 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;
@@ -773,28 +774,44 @@ static void __do_notify(struct mqueue_in
* synchronously. */
if (info->notify_owner &&
info->attr.mq_curmsgs == 1) {
- struct kernel_siginfo sig_i;
switch (info->notify.sigev_notify) {
case SIGEV_NONE:
break;
- case SIGEV_SIGNAL:
- /* sends signal */
+ case SIGEV_SIGNAL: {
+ struct kernel_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);
@@ -1383,6 +1400,7 @@ retry:
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;
}
_
