Patch "net: bridge: fix old ioctl unlocked net device walk" has been added to the 3.14-stable tree

Patch "net: bridge: fix old ioctl unlocked net device walk" has been added to the 3.14-stable tree

[gregkh]

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

    net: bridge: fix old ioctl unlocked net device walk

to the 3.14-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:
     net-bridge-fix-old-ioctl-unlocked-net-device-walk.patch
and it can be found in the queue-3.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Mon May 16 14:28:53 PDT 2016
From: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Date: Wed, 4 May 2016 16:18:45 +0200
Subject: net: bridge: fix old ioctl unlocked net device walk
Status: RO
Content-Length: 2234
Lines: 65

From: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>

[ Upstream commit 31ca0458a61a502adb7ed192bf9716c6d05791a5 ]

get_bridge_ifindices() is used from the old "deviceless" bridge ioctl
calls which aren't called with rtnl held. The comment above says that it is
called with rtnl but that is not really the case.
Here's a sample output from a test ASSERT_RTNL() which I put in
get_bridge_ifindices and executed "brctl show":
[  957.422726] RTNL: assertion failed at net/bridge//br_ioctl.c (30)
[  957.422925] CPU: 0 PID: 1862 Comm: brctl Tainted: G        W  O
4.6.0-rc4+ #157
[  957.423009] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS 1.8.1-20150318_183358- 04/01/2014
[  957.423009]  0000000000000000 ffff880058adfdf0 ffffffff8138dec5
0000000000000400
[  957.423009]  ffffffff81ce8380 ffff880058adfe58 ffffffffa05ead32
0000000000000001
[  957.423009]  00007ffec1a444b0 0000000000000400 ffff880053c19130
0000000000008940
[  957.423009] Call Trace:
[  957.423009]  [<ffffffff8138dec5>] dump_stack+0x85/0xc0
[  957.423009]  [<ffffffffa05ead32>]
br_ioctl_deviceless_stub+0x212/0x2e0 [bridge]
[  957.423009]  [<ffffffff81515beb>] sock_ioctl+0x22b/0x290
[  957.423009]  [<ffffffff8126ba75>] do_vfs_ioctl+0x95/0x700
[  957.423009]  [<ffffffff8126c159>] SyS_ioctl+0x79/0x90
[  957.423009]  [<ffffffff8163a4c0>] entry_SYSCALL_64_fastpath+0x23/0xc1

Since it only reads bridge ifindices, we can use rcu to safely walk the net
device list. Also remove the wrong rtnl comment above.

Signed-off-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/bridge/br_ioctl.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/net/bridge/br_ioctl.c
+++ b/net/bridge/br_ioctl.c
@@ -21,18 +21,19 @@
 #include <asm/uaccess.h>
 #include "br_private.h"
 
-/* called with RTNL */
 static int get_bridge_ifindices(struct net *net, int *indices, int num)
 {
 	struct net_device *dev;
 	int i = 0;
 
-	for_each_netdev(net, dev) {
+	rcu_read_lock();
+	for_each_netdev_rcu(net, dev) {
 		if (i >= num)
 			break;
 		if (dev->priv_flags & IFF_EBRIDGE)
 			indices[i++] = dev->ifindex;
 	}
+	rcu_read_unlock();
 
 	return i;
 }


Patches currently in stable-queue which might be from nikolay@cumulusnetworks.com are

queue-3.14/net-bridge-fix-old-ioctl-unlocked-net-device-walk.patch