[PATCH] audit: fix size of netlink messages
Eric Paris
eparis at redhat.com
Fri Jun 7 15:43:01 UTC 2013
On Fri, 2013-06-07 at 17:25 +0200, Nicolas Dichtel wrote:
NAK.
I tried this once before and as I recal userspace actually expected the
stoopidity of being unaligned and broke :-(
> 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);
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