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authorRichard Guy Briggs <rgb@redhat.com>2016-01-25 18:04:15 -0500
committerPaul Moore <paul@paul-moore.com>2016-01-25 18:04:15 -0500
commit133e1e5acd4a63c4a0dcc413e90d5decdbce9c4a (patch)
tree5f99e8eef18d42363aeebca7424af612c4d6dfaa /kernel/audit.c
parentcb74ed278f8054fddf79ed930495b9e214f7c7b2 (diff)
downloadlinux-sh-133e1e5acd4a63c4a0dcc413e90d5decdbce9c4a.tar.gz
audit: stop an old auditd being starved out by a new auditd
Nothing prevents a new auditd starting up and replacing a valid audit_pid when an old auditd is still running, effectively starving out the old auditd since audit_pid no longer points to the old valid auditd. If no message to auditd has been attempted since auditd died unnaturally or got killed, audit_pid will still indicate it is alive. There isn't an easy way to detect if an old auditd is still running on the existing audit_pid other than attempting to send a message to see if it fails. An -ECONNREFUSED almost certainly means it disappeared and can be replaced. Other errors are not so straightforward and may indicate transient problems that will resolve themselves and the old auditd will recover. Yet others will likely need manual intervention for which a new auditd will not solve the problem. Send a new message type (AUDIT_REPLACE) to the old auditd containing a u32 with the PID of the new auditd. If the audit replace message succeeds (or doesn't fail with certainty), fail to register the new auditd and return an error (-EEXIST). This is expected to make the patch preventing an old auditd orphaning a new auditd redundant. V3: Switch audit message type from 1000 to 1300 block. Signed-off-by: Richard Guy Briggs <rgb@redhat.com> Signed-off-by: Paul Moore <pmoore@redhat.com>
Diffstat (limited to 'kernel/audit.c')
-rw-r--r--kernel/audit.c16
1 files changed, 15 insertions, 1 deletions
diff --git a/kernel/audit.c b/kernel/audit.c
index d6dd95cc59e6..2fd63d6879c5 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -809,6 +809,16 @@ static int audit_set_feature(struct sk_buff *skb)
return 0;
}
+static int audit_replace(pid_t pid)
+{
+ struct sk_buff *skb = audit_make_reply(0, 0, AUDIT_REPLACE, 0, 0,
+ &pid, sizeof(pid));
+
+ if (!skb)
+ return -ENOMEM;
+ return netlink_unicast(audit_sock, skb, audit_nlk_portid, 0);
+}
+
static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
{
u32 seq;
@@ -870,9 +880,13 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
}
if (s.mask & AUDIT_STATUS_PID) {
int new_pid = s.pid;
+ pid_t requesting_pid = task_tgid_vnr(current);
- if ((!new_pid) && (task_tgid_vnr(current) != audit_pid))
+ if ((!new_pid) && (requesting_pid != audit_pid))
return -EACCES;
+ if (audit_pid && new_pid &&
+ audit_replace(requesting_pid) != -ECONNREFUSED)
+ return -EEXIST;
if (audit_enabled != AUDIT_OFF)
audit_log_config_change("audit_pid", new_pid, audit_pid, 1);
audit_pid = new_pid;