fs/lock: skip lock owner pid translation in case we are in init_pid_ns

BugLink: https://bugs.launchpad.net/bugs/1836287
[ Upstream commit 826d7bc9f013d01e92997883d2fd0c25f4af1f1c ]

If the flock owner process is dead and its pid has been already freed,
pid translation won't work, but we still want to show flock owner pid
number when expecting /proc/$PID/fdinfo/$FD in init pidns.

Reproducer:
process A	process A1	process A2
fork()--------->
exit()		open()
		flock()
		fork()--------->
		exit()		sleep()

Before the patch:
================
(root@vz7)/: cat /proc/${PID_A2}/fdinfo/3
pos:    4
flags:  02100002
mnt_id: 257
lock:   (root@vz7)/:

After the patch:
===============
(root@vz7)/:cat /proc/${PID_A2}/fdinfo/3
pos:    4
flags:  02100002
mnt_id: 295
lock:   1: FLOCK  ADVISORY  WRITE ${PID_A1} b6:f8a61:529946 0 EOF

Fixes: 9d5b86ac13c5 ("fs/locks: Remove fl_nspid and use fs-specific l_pid for remote locks")
Signed-off-by: Konstantin Khorenko <khorenko@virtuozzo.com>
Acked-by: Andrey Vagin <avagin@openvz.org>
Reviewed-by: Benjamin Coddington <bcodding@redhat.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/fs/locks.c b/fs/locks.c
index 21b4dfa289eea6e6575c78e966efa691eaeff494..a4ca3d07ea347f50bfaa0dd7ad6fa9410d196535 100644 (file)
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -2074,6 +2074,13 @@ static pid_t locks_translate_pid(struct file_lock *fl, struct pid_namespace *ns)
                return -1;
        if (IS_REMOTELCK(fl))
                return fl->fl_pid;
+       /*
+        * If the flock owner process is dead and its pid has been already
+        * freed, the translation below won't work, but we still want to show
+        * flock owner pid number in init pidns.
+        */
+       if (ns == &init_pid_ns)
+               return (pid_t)fl->fl_pid;
 
        rcu_read_lock();
        pid = find_pid_ns(fl->fl_pid, &init_pid_ns);