Patch "tcp: fix potential huge kmalloc() calls in TCP_REPAIR" has been added to the 4.2-stable tree

This is a note to let you know that I've just added the patch titled

tcp: fix potential huge kmalloc() calls in TCP_REPAIR

to the 4.2-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
tcp-fix-potential-huge-kmalloc-calls-in-tcp_repair.patch
and it can be found in the queue-4.2 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Eric Dumazet <[email protected]>
Date: Wed, 18 Nov 2015 21:03:33 -0800
Subject: tcp: fix potential huge kmalloc() calls in TCP_REPAIR

From: Eric Dumazet <[email protected]>

[ Upstream commit 5d4c9bfbabdb1d497f21afd81501e5c54b0c85d9 ]

tcp_send_rcvq() is used for re-injecting data into tcp receive queue.

Problems :

- No check against size is performed, allowed user to fool kernel in attempting very large memory allocations, eventually triggering OOM when memory is fragmented.

- In case of fault during the copy we do not return correct errno.

Lets use alloc_skb_with_frags() to cook optimal skbs.

---
 net/ipv4/tcp_input.c |   22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

@@ -4434,19 +4434,34 @@ static int __must_check tcp_queue_rcv(st
 int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size)
 {
 	struct sk_buff *skb;
+	int err = -ENOMEM;
+	int data_len = 0;
 	bool fragstolen;
 
 	if (size == 0)
 		return 0;
 
-	skb = alloc_skb(size, sk->sk_allocation);
+	if (size > PAGE_SIZE) {
+		int npages = min_t(size_t, size >> PAGE_SHIFT, MAX_SKB_FRAGS);
+
+		data_len = npages << PAGE_SHIFT;
+		size = data_len + (size & ~PAGE_MASK);
+	}
+	skb = alloc_skb_with_frags(size - data_len, data_len,
+				   PAGE_ALLOC_COSTLY_ORDER,
+				   &err, sk->sk_allocation);
 	if (!skb)
 		goto err;
 
+	skb_put(skb, size - data_len);
+	skb->data_len = data_len;
+	skb->len = size;
+
 	if (tcp_try_rmem_schedule(sk, skb, skb->truesize))
 		goto err_free;
 
-	if (memcpy_from_msg(skb_put(skb, size), msg, size))
+	err = skb_copy_datagram_from_iter(skb, 0, &msg->msg_iter, size);
+	if (err)
 		goto err_free;
 
 	TCP_SKB_CB(skb)->seq = tcp_sk(sk)->rcv_nxt;

@@ -4462,7 +4477,8 @@ int tcp_send_rcvq(struct sock *sk, struc
 err_free:
 	kfree_skb(skb);
 err:
-	return -ENOMEM;
+	return err;
+
 }
 
 static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)

Patches currently in stable-queue which might be from [email protected] are

queue-4.2/ipv6-add-complete-rcu-protection-around-np-opt.patch queue-4.2/packet-infer-protocol-from-ethernet-header-if-unset.patch queue-4.2/af-unix-passcred-support-for-sendpage.patch queue-4.2/ipv6-sctp-implement-sctp_v6_destroy_sock.patch queue-4.2/af_unix-don-t-append-consumed-skbs-to-sk_receive_queue.patch queue-4.2/tcp-disable-fast-open-on-timeouts-after-handshake.patch queue-4.2/net-scm-fix-pax-detected-msg_controllen-overflow-in-scm_detach_fds.patch queue-4.2/tcp-md5-fix-lockdep-annotation.patch queue-4.2/af-unix-fix-use-after-free-with-concurrent-readers-while-splicing.patch queue-4.2/net_sched-fix-qdisc_tree_decrease_qlen-races.patch queue-4.2/tcp-initialize-tp-copied_seq-in-case-of-cross-syn-connection.patch queue-4.2/tcp-fix-potential-huge-kmalloc-calls-in-tcp_repair.patch queue-4.2/packet-do-skb_probe_transport_header-when-we-actually-have-data.patch queue-4.2/af_unix-take-receive-queue-lock-while-appending-new-skb.patch