[rh7,1/2] fs/lock: skip lock owner pid translation in case we are in init_pid_ns

Submitted by Konstantin Khorenko on June 8, 2018, 9:41 a.m.

Details

Message ID 20180608094146.17159-2-khorenko@virtuozzo.com
State New
Series "fs/lock: show locks info owned by dead/invisible processes"
Headers show

Commit Message

Konstantin Khorenko June 8, 2018, 9:41 a.m.
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:

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================
(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

https://jira.sw.ru/browse/PSBM-85651

Signed-off-by: Konstantin Khorenko <khorenko@virtuozzo.com>
---
 fs/locks.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/locks.c b/fs/locks.c
index 5d3aefe920d4..29650e7dcd64 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -1996,6 +1996,13 @@  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);