[3.13.y.z extended stable] Patch "net: cdc_mbim: __vlan_find_dev_deep need rcu_read_lock" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    net: cdc_mbim: __vlan_find_dev_deep need rcu_read_lock

to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11.4.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From f4f43912f6a3a1c71db60006a32501c9de0ba5b9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B8rn=20Mork?= <bjorn at mork.no>
Date: Sat, 3 May 2014 16:12:47 +0200
Subject: net: cdc_mbim: __vlan_find_dev_deep need rcu_read_lock
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

[ Upstream commit 4f4178f3bb1f470d7fb863ec531e08e20a0fd51c ]

Fixes this warning introduced by commit 5b8f15f78e6f
("net: cdc_mbim: handle IPv6 Neigbor Solicitations"):

===============================
[ INFO: suspicious RCU usage. ]
3.15.0-rc3 #213 Tainted: G        W  O
-------------------------------
net/8021q/vlan_core.c:69 suspicious rcu_dereference_check() usage!

other info that might help us debug this:

rcu_scheduler_active = 1, debug_locks = 1
no locks held by ksoftirqd/0/3.

stack backtrace:
CPU: 0 PID: 3 Comm: ksoftirqd/0 Tainted: G        W  O  3.15.0-rc3 #213
Hardware name: LENOVO 2776LEG/2776LEG, BIOS 6EET55WW (3.15 ) 12/19/2011
 0000000000000001 ffff880232533bf0 ffffffff813a5ee6 0000000000000006
 ffff880232530090 ffff880232533c20 ffffffff81076b94 0000000000000081
 0000000000000000 ffff8802085ac000 ffff88007fc8ea00 ffff880232533c50
Call Trace:
 [<ffffffff813a5ee6>] dump_stack+0x4e/0x68
 [<ffffffff81076b94>] lockdep_rcu_suspicious+0xfa/0x103
 [<ffffffff813978a6>] __vlan_find_dev_deep+0x54/0x94
 [<ffffffffa04a1938>] cdc_mbim_rx_fixup+0x379/0x66a [cdc_mbim]
 [<ffffffff813ab76f>] ? _raw_spin_unlock_irqrestore+0x3a/0x49
 [<ffffffff81079671>] ? trace_hardirqs_on_caller+0x192/0x1a1
 [<ffffffffa059bd10>] usbnet_bh+0x59/0x287 [usbnet]
 [<ffffffff8104067d>] tasklet_action+0xbb/0xcd
 [<ffffffff81040057>] __do_softirq+0x14c/0x30d
 [<ffffffff81040237>] run_ksoftirqd+0x1f/0x50
 [<ffffffff8105f13e>] smpboot_thread_fn+0x172/0x18e
 [<ffffffff8105efcc>] ? SyS_setgroups+0xdf/0xdf
 [<ffffffff810594b0>] kthread+0xb5/0xbd
 [<ffffffff813a84b1>] ? __wait_for_common+0x13b/0x170
 [<ffffffff810593fb>] ? __kthread_parkme+0x5c/0x5c
 [<ffffffff813b147c>] ret_from_fork+0x7c/0xb0
 [<ffffffff810593fb>] ? __kthread_parkme+0x5c/0x5c

Fixes: 5b8f15f78e6f ("net: cdc_mbim: handle IPv6 Neigbor Solicitations")
Signed-off-by: Bjørn Mork <bjorn at mork.no>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/net/usb/cdc_mbim.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/net/usb/cdc_mbim.c b/drivers/net/usb/cdc_mbim.c
index c9f3281..13f7705 100644
--- a/drivers/net/usb/cdc_mbim.c
+++ b/drivers/net/usb/cdc_mbim.c
@@ -204,17 +204,23 @@ static void do_neigh_solicit(struct usbnet *dev, u8 *buf, u16 tci)
 		return;

 	/* need to send the NA on the VLAN dev, if any */
-	if (tci)
+	rcu_read_lock();
+	if (tci) {
 		netdev = __vlan_find_dev_deep(dev->net, htons(ETH_P_8021Q),
 					      tci);
-	else
+		if (!netdev) {
+			rcu_read_unlock();
+			return;
+		}
+	} else {
 		netdev = dev->net;
-	if (!netdev)
-		return;
+	}
+	dev_hold(netdev);
+	rcu_read_unlock();

 	in6_dev = in6_dev_get(netdev);
 	if (!in6_dev)
-		return;
+		goto out;
 	is_router = !!in6_dev->cnf.forwarding;
 	in6_dev_put(in6_dev);

@@ -224,6 +230,8 @@ static void do_neigh_solicit(struct usbnet *dev, u8 *buf, u16 tci)
 				 true /* solicited */,
 				 false /* override */,
 				 true /* inc_opt */);
+out:
+	dev_put(netdev);
 }

 static bool is_neigh_solicit(u8 *buf, size_t len)
--
1.9.1