[PATCH ghak25 v4 3/3] audit: add subj creds to NETFILTER_CFG record to cover async unregister

[Richard Guy Briggs]

Some table unregister actions seem to be initiated by the kernel to
garbage collect unused tables that are not initiated by any userspace
actions.  It was found to be necessary to add the subject credentials to
cover this case to reveal the source of these actions.  A sample record:

  type=NETFILTER_CFG msg=audit(2020-03-11 21:25:21.491:269) : table=nat family=bridge entries=0 op=unregister pid=153 uid=root auid=unset tty=(none) ses=unset subj=system_u:system_r:kernel_t:s0 comm=kworker/u4:2 exe=(null)

Signed-off-by: Richard Guy Briggs <rgb@xxxxxxxxxx>
---
 kernel/auditsc.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index d281c18d1771..d7a45b181be0 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -2557,12 +2557,30 @@ void __audit_log_nfcfg(const char *name, u8 af, unsigned int nentries,
 		       enum audit_nfcfgop op)
 {
 	struct audit_buffer *ab;
+	const struct cred *cred;
+	struct tty_struct *tty;
+	char comm[sizeof(current->comm)];
 
 	ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_NETFILTER_CFG);
 	if (!ab)
 		return;
 	audit_log_format(ab, "table=%s family=%u entries=%u op=%s",
 			 name, af, nentries, audit_nfcfgs[op].s);
+
+	cred = current_cred();
+	tty = audit_get_tty();
+	audit_log_format(ab, " pid=%u uid=%u auid=%u tty=%s ses=%u",
+			 task_pid_nr(current),
+			 from_kuid(&init_user_ns, cred->uid),
+			 from_kuid(&init_user_ns, audit_get_loginuid(current)),
+			 tty ? tty_name(tty) : "(none)",
+			 audit_get_sessionid(current));
+	audit_put_tty(tty);
+	audit_log_task_context(ab); /* subj= */
+	audit_log_format(ab, " comm=");
+	audit_log_untrustedstring(ab, get_task_comm(comm, current));
+	audit_log_d_path_exe(ab, current->mm); /* exe= */
+
 	audit_log_end(ab);
 }
 EXPORT_SYMBOL_GPL(__audit_log_nfcfg);
-- 
1.8.3.1