linux-kernel - Re: [PATCH] Fix race condition about network device name allocation

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Date:	Wed, 13 Jun 2007 12:45:21 +0300
From:	Dan Aloni <da-x@...atomic.org>
To:	Stephen Hemminger <shemminger@...ux-foundation.org>
Cc:	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>,
	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] Fix race condition about network device name allocation

On Mon, May 14, 2007 at 08:58:40AM -0700, Stephen Hemminger wrote:
> Kenji Kaneshige found this race between device removal and
> registration.  On unregister it is possible for the old device to
> exist, because sysfs file is still open.  A new device with 'eth%d'
> will select the same name, but sysfs kobject register will fial.
> 
> The following changes the shutdown order slightly. It hold a removes the sysfs
> entries earlier (on unregister_netdevice), but holds a kobject reference.
> Then when todo runs the actual last put free happens.
> 
> Signed-off-by: Stephen Hemminger <shemminger@...ux-foundation.org>

That patch breaks the bonding driver. After reverting it I avoid this crash:

<6>[1115260.637351] Ethernet Channel Bonding Driver: v3.1.2 (January 20, 2007)
<6>[1115260.637358] bonding: MII link monitoring set to 100 ms
<6>[1115260.637767] bonding: bond0 is being deleted...
<1>[1115260.695812] Unable to handle kernel NULL pointer dereference at 0000000000000020 RIP: 
<1>[1115260.701504]  [<ffffffff802805e2>] __lookup_hash+0x22/0x150
<6>[1115260.709754] PGD 798bf067 PUD 798c4067 PMD 0 
<0>[1115260.714394] Oops: 0000 [1] SMP 
[1]kdb> 
[1]kdb> btc
btc: cpu status: Currently on cpu 1
Available cpus: 0(I), 1
Stack traceback for pid 0
0xffffffff80585420        0        0  1    0   I  0xffffffff80585710  swapper
rsp                rip                Function (args)
0xffffffff8066feb0 0xffffffff8046783f thread_return+0x5e
0xffffffff8066fec0 0xffffffff80469df9 _spin_unlock_irq+0x9
0xffffffff8066ff28 0xffffffff80209176 mwait_idle+0x46
0xffffffff8066ff50 0xffffffff802088e2 enter_idle+0x22
0xffffffff8066ff60 0xffffffff802090bc cpu_idle+0x5c
0xffffffff8066ff80 0xffffffff80207146 rest_init+0x26
0xffffffff8066ff90 0xffffffff80678c1a start_kernel+0x2ea
0xffffffff8066ffc0 0xffffffff8067815f _sinittext+0x15f
Stack traceback for pid 66
0xffff81006a411850       66        1  1    1   R  0xffff81006a411b40 *platform_node
rsp                rip                Function (args)
0xffff81006a46dd98 0xffffffff802805e2 __lookup_hash+0x22
0xffff81006a46de00 0xffffffff80280cba lookup_one_len+0x9a
0xffff81006a46de20 0xffffffff802be671 sysfs_remove_group+0x31
0xffff81006a46de50 0xffffffff8800fe4a [bonding]bond_destroy_sysfs_entry+0x1a
0xffff81006a46de60 0xffffffff88011974 [bonding]bonding_store_bonds+0x214
0xffff81006a46deb0 0xffffffff8037c9d4 class_attr_store+0x24
[1]more> 
0xffff81006a46dec0 0xffffffff802bbe30 sysfs_write_file+0x100
0xffff81006a46df10 0xffffffff80277d7e vfs_write+0xbe
0xffff81006a46df40 0xffffffff80278400 sys_write+0x50
0xffff81006a46df80 0xffffffff80209e6e system_call+0x7e

-- 
Dan Aloni
XIV LTD, http://www.xivstorage.com
da-x (at) monatomic.org, dan (at) xiv.co.il
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