linux-kernel - Re:Re: [PATCH 5.4 39/78] Bluetooth: use correct lock to prevent UAF of hdev object

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Date:   Thu, 17 Jun 2021 20:36:46 +0800 (GMT+08:00)
From:   LinMa <linma@....edu.cn>
To:     "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>
Cc:     linux-kernel <linux-kernel@...r.kernel.org>,
        stable <stable@...r.kernel.org>
Subject: Re:Re: [PATCH 5.4 39/78] Bluetooth: use correct lock to prevent UAF
 of hdev object


Oops, sorry for the delay here. I just forgot to check the mails.

This comment is right, when I submit this patch I mentioned that the replacement of this lock can hang the detaching routine because it needs to wait the release of the lock_sock().

But this does no harm in my testing. In fact, the relevant code can only be executed when removing the controller. I think it can wait for the lock. Moreover, this patch can fix the potential UAF indeed.

> may need further discussion. (wrote in previous mail list

Welcome the additional advise on this. Does this really broken the lock principle?

Regards Lin Ma

在 2021-06-16 23:01:08，"Greg Kroah-Hartman" <gregkh@...uxfoundation.org> 写道：

>On Mon, Jun 14, 2021 at 04:15:02PM +0200, Eric Dumazet wrote:
>> 
>> 
>> On 6/8/21 8:27 PM, Greg Kroah-Hartman wrote:
>> > From: Lin Ma <linma@....edu.cn>
>> > 
>> > commit e305509e678b3a4af2b3cfd410f409f7cdaabb52 upstream.
>> > 
>> > The hci_sock_dev_event() function will cleanup the hdev object for
>> > sockets even if this object may still be in used within the
>> > hci_sock_bound_ioctl() function, result in UAF vulnerability.
>> > 
>> > This patch replace the BH context lock to serialize these affairs
>> > and prevent the race condition.
>> > 
>> > Signed-off-by: Lin Ma <linma@....edu.cn>
>> > Signed-off-by: Marcel Holtmann <marcel@...tmann.org>
>> > Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>> > ---
>> >  net/bluetooth/hci_sock.c |    4 ++--
>> >  1 file changed, 2 insertions(+), 2 deletions(-)
>> > 
>> > --- a/net/bluetooth/hci_sock.c
>> > +++ b/net/bluetooth/hci_sock.c
>> > @@ -755,7 +755,7 @@ void hci_sock_dev_event(struct hci_dev *
>> >  		/* Detach sockets from device */
>> >  		read_lock(&hci_sk_list.lock);
>> >  		sk_for_each(sk, &hci_sk_list.head) {
>> > -			bh_lock_sock_nested(sk);
>> > +			lock_sock(sk);
>> >  			if (hci_pi(sk)->hdev == hdev) {
>> >  				hci_pi(sk)->hdev = NULL;
>> >  				sk->sk_err = EPIPE;
>> > @@ -764,7 +764,7 @@ void hci_sock_dev_event(struct hci_dev *
>> >  
>> >  				hci_dev_put(hdev);
>> >  			}
>> > -			bh_unlock_sock(sk);
>> > +			release_sock(sk);
>> >  		}
>> >  		read_unlock(&hci_sk_list.lock);
>> >  	}
>> > 
>> > 
>> 
>> 
>> This patch is buggy.
>> 
>> lock_sock() can sleep.
>> 
>> But the read_lock(&hci_sk_list.lock) two lines before is not going to allow the sleep.
>> 
>> Hmmm ?
>> 
>> 
>
>Odd, Lin, did you see any problems with your testing of this?
>