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Date:   Fri, 1 Feb 2019 03:57:48 +0000
From:   Al Viro <viro@zeniv.linux.org.uk>
To:     Greg KH <gregkh@linuxfoundation.org>
Cc:     Kees Cook <keescook@chromium.org>,
        Andrew Morton <akpm@linux-foundation.org>,
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Subject: Re: general protection fault in relay_open_buf
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On Thu, Jan 31, 2019 at 11:51:52AM +0100, Greg KH wrote:
> Can you test the patch below?
> 
> thanks,
> 
> greg k-h
> 

> @@ -461,7 +463,7 @@ static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu)
>  		dentry = chan->cb->create_buf_file(NULL, NULL,
>  						   S_IRUSR, buf,
>  						   &chan->is_global);
> -		if (WARN_ON(dentry))
> +		if (IS_ERR_OR_NULL(dentry))
>  			goto free_buf;

Huh?  That makes no sense; is it IS_ERR on error or is it NULL
on error, or what?  Besides, how did it work before?