Commit 54e05edd authored by Richard Guy Briggs's avatar Richard Guy Briggs Committed by Eric Paris

audit: set nlmsg_len for multicast messages.

Report:
	Looking at your example code in
	http://people.redhat.com/rbriggs/audit-multicast-listen/audit-multicast-listen.c,
	it seems that nlmsg_len field in the received messages is supposed to
	contain the length of the header + payload, but it is always set to the
	size of the header only, i.e. 16. The example program works, because
	the printf format specifies the minimum width, not "precision", so it
	simply prints out the payload until the first zero byte. This isn't too
	much of a problem, but precludes the use of recvmmsg, iiuc?

	(gdb) p *(struct nlmsghdr*)nlh
	$14 = {nlmsg_len = 16, nlmsg_type = 1100, nlmsg_flags = 0, nlmsg_seq = 0, nlmsg_pid = 9910}

The only time nlmsg_len would have been updated was at audit_buffer_alloc()
inside audit_log_start() and never updated after.  It should arguably be done
in audit_log_vformat(), but would be more efficient in audit_log_end().
Reported-by: default avatarZbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>
Signed-off-by: default avatarRichard Guy Briggs <rgb@redhat.com>
parent 219ca394
...@@ -1949,6 +1949,7 @@ void audit_log_end(struct audit_buffer *ab) ...@@ -1949,6 +1949,7 @@ void audit_log_end(struct audit_buffer *ab)
} else { } else {
struct nlmsghdr *nlh = nlmsg_hdr(ab->skb); struct nlmsghdr *nlh = nlmsg_hdr(ab->skb);
nlh->nlmsg_len = ab->skb->len;
kauditd_send_multicast_skb(ab->skb); kauditd_send_multicast_skb(ab->skb);
/* /*
...@@ -1960,7 +1961,7 @@ void audit_log_end(struct audit_buffer *ab) ...@@ -1960,7 +1961,7 @@ void audit_log_end(struct audit_buffer *ab)
* protocol between the kaudit kernel subsystem and the auditd * protocol between the kaudit kernel subsystem and the auditd
* userspace code. * userspace code.
*/ */
nlh->nlmsg_len = ab->skb->len - NLMSG_HDRLEN; nlh->nlmsg_len -= NLMSG_HDRLEN;
if (audit_pid) { if (audit_pid) {
skb_queue_tail(&audit_skb_queue, ab->skb); skb_queue_tail(&audit_skb_queue, ab->skb);
......
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