Messages in this thread Patch in this message | | | Date | Fri, 14 Mar 2008 19:40:52 +0100 | From | Thomas Graf <> | Subject | Re: Audit vs netlink interaction problem |
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* Thomas Graf <tgraf@suug.ch> 2008-03-14 19:29 > * Pavel Emelyanov <xemul@openvz.org> 2008-03-14 20:05 > > Hmmm... I'm afraid, that this can break the audit filtering and signal > > auditing. I haven't yet looked deep into it, but it compares the > > task->tgid with this audit_pid for different purposes. If audit_pid > > changes this code will be broken. > > OK, then both pids have to be stored. audit_pid remains as-is but is > no longer used as destination netlink pid. A second pid is stored and > updated whenever a netlink message is received from userspace.
The following patch represents what I mean. Untested!
Index: net-2.6.26/kernel/audit.c =================================================================== --- net-2.6.26.orig/kernel/audit.c 2008-03-14 19:31:53.000000000 +0100 +++ net-2.6.26/kernel/audit.c 2008-03-14 19:38:35.000000000 +0100 @@ -82,6 +82,9 @@ * contains the (non-zero) pid. */ int audit_pid; +/* Actual netlink pid of the userspace process */ +static int audit_nlk_pid; + /* If audit_rate_limit is non-zero, limit the rate of sending audit records * to that number per second. This prevents DoS attacks, but results in * audit records being dropped. */ @@ -347,12 +350,12 @@ skb = skb_dequeue(&audit_skb_queue); wake_up(&audit_backlog_wait); if (skb) { - if (audit_pid) { - int err = netlink_unicast(audit_sock, skb, audit_pid, 0); + if (audit_nlk_pid) { + int err = netlink_unicast(audit_sock, skb, audit_nlk_pid, 0); if (err < 0) { BUG_ON(err != -ECONNREFUSED); /* Shoudn't happen */ - printk(KERN_ERR "audit: *NO* daemon at audit_pid=%d\n", audit_pid); - audit_pid = 0; + printk(KERN_ERR "audit: *NO* daemon at audit_nlk_pid=%d\n", audit_nlk_pid); + audit_nlk_pid = 0; } } else { if (printk_ratelimit()) @@ -623,6 +626,12 @@ sid, 1); audit_pid = new_pid; + + /* + * Netlink pid is only updated here to avoid overwrites + * from potential processes only querying the interface. + */ + audit_nlk_pid = NETLINK_CB(skb).pid; } if (status_get->mask & AUDIT_STATUS_RATE_LIMIT) err = audit_set_rate_limit(status_get->rate_limit, @@ -1350,7 +1359,7 @@ if (!audit_rate_check()) { audit_log_lost("rate limit exceeded"); } else { - if (audit_pid) { + if (audit_nlk_pid) { struct nlmsghdr *nlh = nlmsg_hdr(ab->skb); nlh->nlmsg_len = ab->skb->len - NLMSG_SPACE(0); skb_queue_tail(&audit_skb_queue, ab->skb);
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