@@ -750,6 +750,10 @@ static void netlink_skb_destructor(struct sk_buff *skb)
skb->data = NULL;
}
#endif
+ if (is_vmalloc_addr(skb->head)) {
+ vfree(skb->head);
+ skb->data = NULL;
+ }
if (skb->sk != NULL)
sock_rfree(skb);
}
@@ -1420,6 +1424,35 @@ struct sock *netlink_getsockbyfilp(struct file *filp)
return sock;
}
+static struct sk_buff *netlink_alloc_large_skb(unsigned int size)
+{
+ struct sk_buff *skb;
+ void *data;
+
+ if (size <= PAGE_SIZE)
+ return alloc_skb(size, GFP_KERNEL);
+
+ skb = alloc_skb_head(GFP_KERNEL);
+ if (skb == NULL)
+ return NULL;
+
+ data = vmalloc(size);
+ if (data == NULL)
+ goto err;
+
+ skb->head = data;
+ skb->data = data;
+ skb_reset_tail_pointer(skb);
+ skb->end = skb->tail + size;
+ skb->len = 0;
+ skb->destructor = netlink_skb_destructor;
+
+ return skb;
+err:
+ kfree_skb(skb);
+ return NULL;
+}
+
/*
* Attach a skb to a netlink socket.
* The caller must hold a reference to the destination socket. On error, the
@@ -1510,7 +1543,7 @@ static struct sk_buff *netlink_trim(struct sk_buff *skb, gfp_t allocation)
return skb;
delta = skb->end - skb->tail;
- if (delta * 2 < skb->truesize)
+ if (is_vmalloc_addr(skb->head) || delta * 2 < skb->truesize)
return skb;
if (skb_shared(skb)) {
@@ -2096,7 +2129,7 @@ static int netlink_sendmsg(struct kiocb *kiocb, struct socket *sock,
if (len > sk->sk_sndbuf - 32)
goto out;
err = -ENOBUFS;
- skb = alloc_skb(len, GFP_KERNEL);
+ skb = netlink_alloc_large_skb(len);
if (skb == NULL)
goto out;
I can hit ENOBUFS in the sendmsg() path with a large batch that is composed of many netlink messages. Here that limit is 8 MBytes of skbuff data area as kmalloc does not manage to get more than that. While discussing atomic rule-set for nftables with Patrick McHardy, we decided to put all rule-set updates that need to be applied atomically in one single batch to simplify the existing approach. However, as explained above, the existing netlink code limits us to a maximum of ~20000 rules that fit in one single batch without hitting ENOBUFS. iptables does not have such limitation as it is using vmalloc. This patch adds netlink_alloc_large_skb() which is only used in the netlink_sendmsg() path. It uses alloc_skb if the memory requested is <= one memory page, that should be the common case for most subsystems, else vmalloc for higher memory allocations. Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> --- net/netlink/af_netlink.c | 37 +++++++++++++++++++++++++++++++++++-- 1 file changed, 35 insertions(+), 2 deletions(-)