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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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netlink: allow large data transfers from user-space
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> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -750,6 +750,10 @@ static void netlink_skb_destructor(struct sk_buff *skb)
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skb->head = NULL;
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skb->head = NULL;
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}
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}
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#endif
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#endif
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if (is_vmalloc_addr(skb->head)) {
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vfree(skb->head);
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skb->head = NULL;
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}
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if (skb->sk != NULL)
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if (skb->sk != NULL)
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sock_rfree(skb);
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sock_rfree(skb);
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}
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}
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@ -1420,6 +1424,35 @@ struct sock *netlink_getsockbyfilp(struct file *filp)
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return sock;
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return sock;
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}
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}
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static struct sk_buff *netlink_alloc_large_skb(unsigned int size)
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{
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struct sk_buff *skb;
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void *data;
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if (size <= NLMSG_GOODSIZE)
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return alloc_skb(size, GFP_KERNEL);
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skb = alloc_skb_head(GFP_KERNEL);
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if (skb == NULL)
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return NULL;
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data = vmalloc(size);
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if (data == NULL)
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goto err;
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skb->head = data;
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skb->data = data;
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skb_reset_tail_pointer(skb);
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skb->end = skb->tail + size;
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skb->len = 0;
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skb->destructor = netlink_skb_destructor;
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return skb;
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err:
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kfree_skb(skb);
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return NULL;
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}
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/*
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/*
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* Attach a skb to a netlink socket.
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* Attach a skb to a netlink socket.
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* The caller must hold a reference to the destination socket. On error, the
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* The caller must hold a reference to the destination socket. On error, the
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@ -1510,7 +1543,7 @@ static struct sk_buff *netlink_trim(struct sk_buff *skb, gfp_t allocation)
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return skb;
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return skb;
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delta = skb->end - skb->tail;
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delta = skb->end - skb->tail;
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if (delta * 2 < skb->truesize)
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if (is_vmalloc_addr(skb->head) || delta * 2 < skb->truesize)
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return skb;
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return skb;
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if (skb_shared(skb)) {
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if (skb_shared(skb)) {
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@ -2096,7 +2129,7 @@ static int netlink_sendmsg(struct kiocb *kiocb, struct socket *sock,
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if (len > sk->sk_sndbuf - 32)
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if (len > sk->sk_sndbuf - 32)
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goto out;
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goto out;
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err = -ENOBUFS;
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err = -ENOBUFS;
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skb = alloc_skb(len, GFP_KERNEL);
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skb = netlink_alloc_large_skb(len);
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if (skb == NULL)
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if (skb == NULL)
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goto out;
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goto out;
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