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From: LinMa <3160105373@zju.edu.cn>
To: "Tetsuo Handa" <penguin-kernel@i-love.sakura.ne.jp>
Cc: "Desmond Cheong Zhi Xi" <desmondcheongzx@gmail.com>,
	"Luiz Augusto von Dentz" <luiz.dentz@gmail.com>,
	"Johan Hedberg" <johan.hedberg@gmail.com>,
	"Marcel Holtmann" <marcel@holtmann.org>,
	"linux-bluetooth@vger.kernel.org"
	<linux-bluetooth@vger.kernel.org>,
	"David S. Miller" <davem@davemloft.net>,
	"Jakub Kicinski" <kuba@kernel.org>,
	"open list:NETWORKING [GENERAL]" <netdev@vger.kernel.org>
Subject: Re: Re: [PATCH v3] Bluetooth: call lock_sock() outside of spinlock section
Date: Fri, 16 Jul 2021 23:26:47 +0800 (GMT+08:00)	[thread overview]
Message-ID: <4bd89382.4d087.17aafed62b1.Coremail.3160105373@zju.edu.cn> (raw)
In-Reply-To: <e07c5bbf-115c-6ffa-8492-7b749b9d286b@i-love.sakura.ne.jp>

Hello everyone,

Sorry, it's my fault to cause the misunderstanding.

As I keep mentioning "hci_sock_sendmsg()" instead of "hci_sock_bound_ioctl()". In fact, both these two functions are able to cause the race.

> >>
> > 
> > My bad, was thinking more about the problem and noticed your poc was for hci_sock_sendmsg,
> > not hci_sock_dev_event.
> 
> I didn't catch this part. Are you talking about a different poc?
> As far as I'm aware, exp.c in POC.zip was for hci_sock_bound_ioctl(HCIUNBLOCKADDR).
> 
> hci_sock_bound_ioctl(HCIUNBLOCKADDR) (which is called between lock_sock() and release_sock())
> calls copy_from_user() which might cause page fault, and userfaultfd mechanism allows an attacker
> to slowdown page fault handling enough to hci_sock_dev_event(HCI_DEV_UNREG) to return without
> waiting for hci_sock_bound_ioctl(HCIUNBLOCKADDR) to call release_sock(). This race window
> results in UAF (doesn't it, LinMa?).
> 

Your understanding above is quite right. In addition, because the hci_sock_sendmsg() calls the memcpy_from_msg(...), which also in fact fetch data from userspace memory, the userfaultfd can take effect as well.

(When writing the exploit for this CVE, the hci_sock_sendmsg() is much useful... so I recently keep mentioning this function)

Regards
Lin Ma

  reply	other threads:[~2021-07-16 15:27 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-27 13:11 [PATCH] " Tetsuo Handa
2021-07-07  9:43 ` [PATCH v2] " Tetsuo Handa
2021-07-07 18:20   ` Luiz Augusto von Dentz
2021-07-07 23:33     ` Tetsuo Handa
2021-07-08  1:00       ` LinMa
2021-07-09 13:50         ` Tetsuo Handa
2021-07-10 13:34       ` Tetsuo Handa
2021-07-13 11:27   ` [PATCH v3] " Tetsuo Handa
2021-07-14 19:20     ` Luiz Augusto von Dentz
2021-07-15  3:03       ` LinMa
2021-07-16  3:47         ` Desmond Cheong Zhi Xi
2021-07-16  4:11           ` Desmond Cheong Zhi Xi
2021-07-16 14:48             ` Tetsuo Handa
2021-07-16 15:26               ` LinMa [this message]
2021-07-17 15:41                 ` Yet Another Patch for CVE-2021-3573 LinMa
2021-07-17 15:45                   ` LinMa
2021-07-22  9:36                 ` [PATCH v3] Bluetooth: call lock_sock() outside of spinlock section Tetsuo Handa
2021-07-22  4:47               ` LinMa
2021-07-22  5:16                 ` Tetsuo Handa

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