[PATCH AUTOSEL for 4.14 60/64] audit: Allow auditd to set pid to 0 to end auditing

From: alexander . levin
Date: Sat Dec 02 2017 - 11:07:03 EST


From: Steve Grubb <sgrubb@xxxxxxxxxx>

[ Upstream commit 33e8a907804428109ce1d12301c3365d619cc4df ]

The API to end auditing has historically been for auditd to set the
pid to 0. This patch restores that functionality.

See: https://github.com/linux-audit/audit-kernel/issues/69

Reviewed-by: Richard Guy Briggs <rgb@xxxxxxxxxx>
Signed-off-by: Steve Grubb <sgrubb@xxxxxxxxxx>
Signed-off-by: Paul Moore <paul@xxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
---
kernel/audit.c | 29 ++++++++++++++++-------------
1 file changed, 16 insertions(+), 13 deletions(-)

diff --git a/kernel/audit.c b/kernel/audit.c
index be1c28fd4d57..d779326e53c0 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -1197,25 +1197,28 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
pid_t auditd_pid;
struct pid *req_pid = task_tgid(current);

- /* sanity check - PID values must match */
- if (new_pid != pid_vnr(req_pid))
+ /* Sanity check - PID values must match. Setting
+ * pid to 0 is how auditd ends auditing. */
+ if (new_pid && (new_pid != pid_vnr(req_pid)))
return -EINVAL;

/* test the auditd connection */
audit_replace(req_pid);

auditd_pid = auditd_pid_vnr();
- /* only the current auditd can unregister itself */
- if ((!new_pid) && (new_pid != auditd_pid)) {
- audit_log_config_change("audit_pid", new_pid,
- auditd_pid, 0);
- return -EACCES;
- }
- /* replacing a healthy auditd is not allowed */
- if (auditd_pid && new_pid) {
- audit_log_config_change("audit_pid", new_pid,
- auditd_pid, 0);
- return -EEXIST;
+ if (auditd_pid) {
+ /* replacing a healthy auditd is not allowed */
+ if (new_pid) {
+ audit_log_config_change("audit_pid",
+ new_pid, auditd_pid, 0);
+ return -EEXIST;
+ }
+ /* only current auditd can unregister itself */
+ if (pid_vnr(req_pid) != auditd_pid) {
+ audit_log_config_change("audit_pid",
+ new_pid, auditd_pid, 0);
+ return -EACCES;
+ }
}

if (new_pid) {
--
2.11.0