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

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Message-ID: <593E20A1.10608@huawei.com>
Date:   Mon, 12 Jun 2017 13:03:29 +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>,
        zhongjiang <zhongjiang@...wei.com>
Subject: Re: [PATCH] fs: fcntl, avoid undefined behaviour

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?

Thanks
zhongjiang