linux-kernel - Re: [PATCH] fs: fcntl, avoid undefined behaviour

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Message-ID: <593FB839.2070804@huawei.com>
Date:   Tue, 13 Jun 2017 18:02:33 +0800
From:   zhong jiang <zhongjiang@...wei.com>
To:     Jiri Slaby <jslaby@...e.cz>
CC:     <viro@...iv.linux.org.uk>, <linux-kernel@...r.kernel.org>,
        Jeff Layton <jlayton@...chiereds.net>,
        "J. Bruce Fields" <bfields@...ldses.org>,
        <linux-fsdevel@...r.kernel.org>, Xishi Qiu <qiuxishi@...wei.com>
Subject: Re: [PATCH] fs: fcntl, avoid undefined behaviour

On 2017/6/13 17:29, Jiri Slaby wrote:
> On 06/12/2017, 07:03 AM, zhong jiang wrote:
>> On 2016/10/14 17:23, Jiri Slaby wrote:
>>> fcntl(0, F_SETOWN, 0x80000000) triggers:
>>> UBSAN: Undefined behaviour in fs/fcntl.c:118:7
>>> negation of -2147483648 cannot be represented in type 'int':
>>> CPU: 1 PID: 18261 Comm: syz-executor Not tainted 4.8.1-0-syzkaller #1
>>> ...
>>> Call Trace:
>>> ...
>>>  [<ffffffffad8f0868>] ? f_setown+0x1d8/0x200
>>>  [<ffffffffad8f19a9>] ? SyS_fcntl+0x999/0xf30
>>>  [<ffffffffaed1fb00>] ? entry_SYSCALL_64_fastpath+0x23/0xc1
>>>
>>> Fix that by checking the arg parameter properly (against INT_MAX) and
>>> return immediatelly in case it is wrong. No error is returned, the
>>> same as in other cases.
>>>
>>> Signed-off-by: Jiri Slaby <jslaby@...e.cz>
>>> Cc: Jeff Layton <jlayton@...chiereds.net>
>>> Cc: "J. Bruce Fields" <bfields@...ldses.org>
>>> Cc: Alexander Viro <viro@...iv.linux.org.uk>
>>> Cc: linux-fsdevel@...r.kernel.org
>>> ---
>>>  fs/fcntl.c | 4 ++++
>>>  1 file changed, 4 insertions(+)
>>>
>>> diff --git a/fs/fcntl.c b/fs/fcntl.c
>>> index 350a2c8cfd28..bfc3b040d956 100644
>>> --- a/fs/fcntl.c
>>> +++ b/fs/fcntl.c
>>> @@ -112,6 +112,10 @@ void f_setown(struct file *filp, unsigned long arg, int force)
>>>  	enum pid_type type;
>>>  	struct pid *pid;
>>>  	int who = arg;
>>> +
>>> +	if (arg > INT_MAX)
>>> +		return;
>>> +
>>>  	type = PIDTYPE_PID;
>>>  	if (who < 0
>>>  		type = PIDTYPE_PGID;
>> Hi, Jiri
>>
>> I hit the same issue,  but I see the upstream is still not changed.  Had any problem?
> Hi, it needed an update which I have just sent. So let's see if that
> gets applied.
>
> thanks,
  I have updated in newest kernel version. but it fails to get the change.  Can you look at that?

Thanks
zhongjiang