Commit 31ca0458 authored May 04, 2016 by Nikolay Aleksandrov Committed by David S. Miller May 05, 2016

net: bridge: fix old ioctl unlocked net device walk



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>

parent dedc58e0

net/bridge/br_ioctl.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -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;
		}

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