lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <db571c6a-0a99-0334-e910-c0bfdb919e72@redhat.com>
Date:   Tue, 23 Apr 2019 14:42:43 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     YueHaibing <yuehaibing@...wei.com>, netdev <netdev@...r.kernel.org>
Subject: Re: BUG: KASAN: use-after-free Read in tun_net_xmit


On 2019/4/23 下午2:00, Cong Wang wrote:
> On Mon, Apr 22, 2019 at 2:41 AM Jason Wang <jasowang@...hat.com> wrote:
>>
>> On 2019/4/22 上午11:57, YueHaibing wrote:
>>> We get a KASAN report as below, but don't have any reproducer.
>>>
>>> Any comments are appreciated.
>>>
>>> ==================================================================
>>> BUG: KASAN: use-after-free in tun_net_xmit+0x1670/0x1750 drivers/net/tun.c:1104
>>> Read of size 8 at addr ffff88836cc26a70 by task swapper/3/0
>>
>> Which kernel version did you use? The calltrace points out the a use
>> after free for tun_file structure which should be synchronized through
>> RCU + RTNL lock.
> The tfile socket has to be marked with SOCK_RCU_FREE in order
> to fully respect the RCU grace period.
>
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index e9ca1c088d0b..31c3210288cb 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -3431,6 +3431,7 @@ static int tun_chr_open(struct inode *inode,
> struct file * file)
>          file->private_data = tfile;
>          INIT_LIST_HEAD(&tfile->next);
>
> +       sock_set_flag(&tfile->sk, SOCK_RCU_FREE);
>          sock_set_flag(&tfile->sk, SOCK_ZEROCOPY);
>
>          return 0;


We did a synchronize_net() when socket is detached from netdevice in 
__tun_detach() so it looks to me this is unnecessary.

But if it solves the use-after-free, it means we have bugs somewhere.

Thanks

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ