[PATCH] audit: fix size of netlink messages

[Nicolas Dichtel]

Netlink messages must be aligned on NLMSG_ALIGNTO (4 bytes), thus we need to
update the skb length before sending it to userspace.

This patch adds the needed padding to be compliant with this requirement.

Signed-off-by: Nicolas Dichtel <nicolas.dichtel at 6wind.com>
---
 kernel/audit.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/kernel/audit.c b/kernel/audit.c
index 21c7fa6..31d213a 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -1669,6 +1669,17 @@ void audit_log_end(struct audit_buffer *ab)
 		struct nlmsghdr *nlh = nlmsg_hdr(ab->skb);
 		nlh->nlmsg_len = ab->skb->len - NLMSG_HDRLEN;
 
+		if (NLMSG_ALIGN(ab->skb->len) != ab->skb->len) {
+			unsigned int pad = NLMSG_ALIGN(ab->skb->len) -
+					   ab->skb->len;
+
+			if (skb_tailroom(ab->skb) >= pad)
+				skb_put(ab->skb, pad);
+			else if (pskb_expand_head(ab->skb, 0, pad,
+						  GFP_KERNEL) < 0)
+				audit_log_lost("out of memory in audit_log_end");
+		}
+
 		if (audit_pid) {
 			skb_queue_tail(&audit_skb_queue, ab->skb);
 			wake_up_interruptible(&kauditd_wait);
-- 
1.8.2.1