[PATCH net] caif: Fix access to freed pernet memory

From: Sjur Brændeland <redacted>

unregister_netdevice_notifier() must be called before
unregister_pernet_subsys() to avoid accessing already freed
pernet memory. This fixes the following oops when doing rmmod:

Call Trace:
 [<ffffffffa0f802bd>] caif_device_notify+0x4d/0x5a0 [caif]
 [<ffffffff81552ba9>] unregister_netdevice_notifier+0xb9/0x100
 [<ffffffffa0f86dcc>] caif_device_exit+0x1c/0x250 [caif]
 [<ffffffff810e7734>] sys_delete_module+0x1a4/0x300
 [<ffffffff810da82d>] ? trace_hardirqs_on_caller+0x15d/0x1e0
 [<ffffffff813517de>] ? trace_hardirqs_on_thunk+0x3a/0x3
 [<ffffffff81696bad>] system_call_fastpath+0x1a/0x1f

RIP
 [<ffffffffa0f7f561>] caif_get+0x51/0xb0 [caif]

Signed-off-by: Sjur Brændeland <redacted>
---

Hi Dave,

Can you please queue up this bugfix as appropriate for -net and -stable?

I guess this bug has been around since introduction of network
name spaces in CAIF, but it became visible after 3.4 and the commit:
"net: In unregister_netdevice_notifier unregister the netdevices." 

Thanks,
Sjur

 net/caif/caif_dev.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/net/caif/caif_dev.c b/net/caif/caif_dev.c
index 554b312..8c83c17 100644
--- a/net/caif/caif_dev.c
+++ b/net/caif/caif_dev.c

@@ -561,9 +561,9 @@ static int __init caif_device_init(void)
 
 static void __exit caif_device_exit(void)
 {
-	unregister_pernet_subsys(&caif_net_ops);
 	unregister_netdevice_notifier(&caif_device_notifier);
 	dev_remove_pack(&caif_packet_type);
+	unregister_pernet_subsys(&caif_net_ops);
 }
 
 module_init(caif_device_init);

-- 
1.7.5.4

sjur.brandeland@stericsson.com writes:

From: Sjur Brændeland <redacted>

unregister_netdevice_notifier() must be called before
unregister_pernet_subsys() to avoid accessing already freed
pernet memory. This fixes the following oops when doing rmmod:

Acked-by: "Eric W. Biederman" <redacted>

The patch looks good to me.

You might want to look at error handling during caif_device_init
as well, as it looks like the same ordering issue is present.
Although unlikely to bite anyone at that point.

Eric

From: sjur.brandeland@stericsson.com
Date: Sun, 15 Jul 2012 22:10:14 +0200

Can you please queue up this bugfix as appropriate for -net and -stable?

Done.