linux-kernel - Re: general protection fault in relay_open

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Message-ID: <20190201035748.GL2217@ZenIV.linux.org.uk>
Date:   Fri, 1 Feb 2019 03:57:48 +0000
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Kees Cook <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        syzbot <syzbot+16c3a70e1e9b29346c43@...kaller.appspotmail.com>,
        Eric Biggers <ebiggers@...gle.com>,
        Souptick Joarder <jrdr.linux@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        David Rientjes <rientjes@...gle.com>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>
Subject: Re: general protection fault in relay_open_buf

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?