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Allow systemd-journald to use kill(pid, 0) on its clients 

Since systemd 241, systemd-journald is using kill(pid, 0) in order to
find dead processes and reduce its cache. The relevant commit is
91714a7f42
("journald: periodically drop cache for all dead PIDs"). This commit
added a call to pid_is_unwaited(c->pid), which is a function implemented in
https://github.com/systemd/systemd/blob/v241/src/basic/process-util.c#L936 :

    bool pid_is_unwaited(pid_t pid) {
        /* Checks whether a PID is still valid at all, including a zombie */
        if (pid < 0)
                return false;
        if (pid <= 1) /* If we or PID 1 would be dead and have been waited for, this code would not be running */
                return true;
        if (pid == getpid_cached())
                return true;
        if (kill(pid, 0) >= 0)
                return true;
        return errno != ESRCH;
    }

This new code triggers the following AVC denials:

    type=AVC msg=audit(1550911933.606:332): avc:  denied  { signull }
    for  pid=224 comm="systemd-journal"
    scontext=system_u:system_r:syslogd_t
    tcontext=system_u:system_r:auditd_t tclass=process permissive=1

    type=AVC msg=audit(1550911933.606:333): avc:  denied  { signull }
    for  pid=224 comm="systemd-journal"
    scontext=system_u:system_r:syslogd_t
    tcontext=system_u:system_r:dhcpc_t tclass=process permissive=1

    type=AVC msg=audit(1550911933.606:334): avc:  denied  { signull }
    for  pid=224 comm="systemd-journal"
    scontext=system_u:system_r:syslogd_t
    tcontext=system_u:system_r:sshd_t tclass=process permissive=1
This commit is contained in:
Nicolas Iooss 2019-02-23 20:55:17 +01:00
parent 5986fdc4df
commit 5250bd4863
No known key found for this signature in database
GPG Key ID: C191415F340DAAA0
1 changed files with 5 additions and 0 deletions
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5
policy/modules/system/logging.if
View File

@ -638,6 +638,11 @@ interface(`logging_send_syslog_msg',`
# will write to the console.
term_write_console($1)
term_dontaudit_read_console($1)
ifdef(`init_systemd',`
# Allow systemd-journald to check whether the process died
allow syslogd_t $1:process signull;
')
')
########################################