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    Subject[PATCH AUTOSEL 4.14 83/87] fs/lock: skip lock owner pid translation in case we are in init_pid_ns
    Date
    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:
    ================
    (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>
    ---
    fs/locks.c | 7 +++++++
    1 file changed, 7 insertions(+)

    diff --git a/fs/locks.c b/fs/locks.c
    index 1bd71c4d663a..665e3ce9ab47 100644
    --- 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);
    --
    2.17.1
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