Put Thomas in CC.
Le 07/06/2013 17:43, Eric Paris a écrit :
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 :-(
On which userspace tools do you think?
For example, in the libnl, the function which tries to get the next netlink
message expects this alignment:
struct nlmsghdr *nlmsg_next(struct nlmsghdr *nlh, int *remaining)
{
int totlen = NLMSG_ALIGN(nlh->nlmsg_len);
*remaining -= totlen;
return (struct nlmsghdr *) ((unsigned char *) nlh + totlen);
}
http://www.infradead.org/~tgr/libnl/doc/core.html#_message_parsing_amp_construction
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 <[email protected]>
---
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) {
Here, I think it's better to use nlmsg_padlen().
+ 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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