Lazy setup of inotify_fd in sd-journal may cause clients to leak file descriptors

[msekletar]

systemd version the issue has been seen with

• git master

Used distribution

• Fedora

Expected behaviour you didn't see

• No deleted files referenced by the sd-journal client after calling sd_journal_process()

Unexpected behaviour you saw

• Files that were deleted by the journald server are still opened by the sd-journal client after calling sd_journal_process(). This is because files were opened by the client and deleted by the server before we've setup inotify monitor.

Steps to reproduce the problem

#!/usr/bin/python3

from systemd import journal
from os import listdir,readlink
from subprocess import run

def list_fds():
    for fd in listdir("/proc/self/fd"):
        try:
            print(f"    {fd} -> {readlink('/proc/self/fd/' + fd)}")
        except FileNotFoundError as e:
            pass
devnull = open("/dev/null", "w")

print("Rotate journal 3 times")
for i in range(3):
    run(["journalctl", "--rotate"], stdout=devnull, stderr=devnull)

print("Open journal")
r = journal.Reader()

print("List fds")
list_fds()

print("Delete some journal files")
run(["journalctl", "--vacuum-files", "1"], stdout=devnull, stderr=devnull)

print("Process journal events")
r.wait(0)

print("List fds")
list_fds()

Example output of the reproducer script

Rotate journal 3 times
Open journal
List fds
    0 -> /dev/pts/0
    1 -> /dev/pts/0
    2 -> /dev/pts/0
    3 -> /dev/null
    6 -> /var/log/journal/56161deef0f24959be056aa81810ce4f/system@3d354d8051214925b8d43f50e63d7307-000000000011eb29-00059d4928d6c3d6.journal
    7 -> /var/log/journal/56161deef0f24959be056aa81810ce4f/system.journal
    8 -> /var/log/journal/56161deef0f24959be056aa81810ce4f/user-1000@aaabf79080ca4edcafc88708e607b702-000000000011ebb7-00059d497ac0ed84.journal
    9 -> /var/log/journal/56161deef0f24959be056aa81810ce4f/system@3d354d8051214925b8d43f50e63d7307-000000000011eca1-00059d49fd720acb.journal
    10 -> /var/log/journal/56161deef0f24959be056aa81810ce4f/user-1001.journal
    11 -> /var/log/journal/56161deef0f24959be056aa81810ce4f/system@3d354d8051214925b8d43f50e63d7307-000000000011eca2-00059d49fd728a75.journal
    12 -> /var/log/journal/56161deef0f24959be056aa81810ce4f/user-1001@cbd42769b3e547cba69261355d9ba2f8-000000000011ec84-00059d49c900efb9.journal
    13 -> /var/log/journal/56161deef0f24959be056aa81810ce4f/user-1000.journal
Delete some journal files
Process journal events
List fds
    0 -> /dev/pts/0
    1 -> /dev/pts/0
    2 -> /dev/pts/0
    3 -> /dev/null
    6 -> /var/log/journal/56161deef0f24959be056aa81810ce4f/system@3d354d8051214925b8d43f50e63d7307-000000000011eb29-00059d4928d6c3d6.journal (deleted)
    7 -> /var/log/journal/56161deef0f24959be056aa81810ce4f/system.journal
    8 -> /var/log/journal/56161deef0f24959be056aa81810ce4f/user-1000@aaabf79080ca4edcafc88708e607b702-000000000011ebb7-00059d497ac0ed84.journal (deleted)
    9 -> /var/log/journal/56161deef0f24959be056aa81810ce4f/system@3d354d8051214925b8d43f50e63d7307-000000000011eca1-00059d49fd720acb.journal (deleted)
    10 -> /var/log/journal/56161deef0f24959be056aa81810ce4f/user-1001.journal
    11 -> /var/log/journal/56161deef0f24959be056aa81810ce4f/system@3d354d8051214925b8d43f50e63d7307-000000000011eca2-00059d49fd728a75.journal (deleted)
    12 -> /var/log/journal/56161deef0f24959be056aa81810ce4f/user-1001@cbd42769b3e547cba69261355d9ba2f8-000000000011ec84-00059d49c900efb9.journal (deleted)
    13 -> /var/log/journal/56161deef0f24959be056aa81810ce4f/user-1000.journal