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From:   Sasha Levin <Alexander.Levin@microsoft.com>
To:     "stable@vger.kernel.org" <stable@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
CC:     Konstantin Khorenko <khorenko@virtuozzo.com>,
        Jeff Layton <jlayton@redhat.com>,
        Sasha Levin <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL 4.18 127/136] fs/lock: skip lock owner pid translation
 in case we are in init_pid_ns
Thread-Topic: [PATCH AUTOSEL 4.18 127/136] fs/lock: skip lock owner pid
 translation in case we are in init_pid_ns
Thread-Index: AQHUTjK872QKClWVSEqFODLTeigUDg==
Date:   Mon, 17 Sep 2018 03:01:31 +0000
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From: Konstantin Khorenko <khorenko@virtuozzo.com>

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

After the patch:
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
(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 f=
or 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>
---
 fs/locks.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/locks.c b/fs/locks.c
index db7b6917d9c5..fafce5a8d74f 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -2072,6 +2072,13 @@ static pid_t locks_translate_pid(struct file_lock *f=
l, 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 =3D=3D &init_pid_ns)
+		return (pid_t)fl->fl_pid;
=20
 	rcu_read_lock();
 	pid =3D find_pid_ns(fl->fl_pid, &init_pid_ns);
--=20
2.17.1