limit allocation size in ieee802154_sock_sendmsg

[Dave Jones <davej@redhat.com>]

Sasha reported this last November (https://lkml.org/lkml/2011/11/22/41)
and I keep walking into it while fuzz testing.

Length of the packet is passed in from userspace, and passed down to the
page allocator unchecked. If the allocation size is bigger than MAX_ORDER,
we get this backtrace from the page allocator.

 WARNING: at mm/page_alloc.c:2298 __alloc_pages_nodemask+0x46d/0xb00()
 Call Trace:
  [<ffffffff81064b2f>] warn_slowpath_common+0x7f/0xc0
  [<ffffffff81064b8a>] warn_slowpath_null+0x1a/0x20
  [<ffffffff8116105d>] __alloc_pages_nodemask+0x46d/0xb00
  [<ffffffff8155ed3b>] ? __alloc_skb+0x4b/0x230
  [<ffffffff810d43dd>] ? trace_hardirqs_on+0xd/0x10
  [<ffffffff816ace3f>] kmalloc_large_node+0x66/0xab
  [<ffffffff811ad9b5>] __kmalloc_node_track_caller+0x1b5/0x200
  [<ffffffff81559701>] ? sock_alloc_send_pskb+0x271/0x3e0
  [<ffffffff8155ed68>] __alloc_skb+0x78/0x230
  [<ffffffff81559701>] sock_alloc_send_pskb+0x271/0x3e0
  [<ffffffff8156d331>] ? dev_getfirstbyhwtype+0x161/0x250
  [<ffffffff8156d1d0>] ? rps_may_expire_flow+0x220/0x220
  [<ffffffff81559885>] sock_alloc_send_skb+0x15/0x20
  [<ffffffffa4a73347>] dgram_sendmsg+0xe7/0x340 [af_802154]
  [<ffffffffa4a72044>] ieee802154_sock_sendmsg+0x14/0x20 [af_802154]
  [<ffffffff81553787>] sock_sendmsg+0x117/0x130
  [<ffffffff810cdb7d>] ? trace_hardirqs_off+0xd/0x10
  [<ffffffff816b81c7>] ? _raw_spin_unlock_irqrestore+0x77/0x80
  [<ffffffff8134312b>] ? debug_object_activate+0x12b/0x1a0
  [<ffffffff816b81c7>] ? _raw_spin_unlock_irqrestore+0x77/0x80
  [<ffffffff81556b60>] sys_sendto+0x140/0x190
  [<ffffffff816c5014>] ? bad_to_user+0x5e/0x80a
  [<ffffffff8133c04e>] ? trace_hardirqs_on_thunk+0x3a/0x3f
  [<ffffffff816c15e9>] system_call_fastpath+0x16/0x1b

Signed-off-by: Dave Jones <davej@redhat.com>

diff --git a/net/ieee802154/af_ieee802154.c b/net/ieee802154/af_ieee802154.c
index 40e606f..1da228a 100644
--- a/net/ieee802154/af_ieee802154.c
+++ b/net/ieee802154/af_ieee802154.c
@@ -108,6 +108,9 @@ static int ieee802154_sock_sendmsg(struct kiocb *iocb, struct socket *sock,
 {
 	struct sock *sk = sock->sk;
 
+	if (len > MAX_ORDER_NR_PAGES * PAGE_SIZE)
+		return -EINVAL;
+
 	return sk->sk_prot->sendmsg(iocb, sk, msg, len);
 }