linux-kernel - Re: [PATCH] pstore/blk: Use the normal block device I/O path

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Date:   Mon, 14 Jun 2021 20:09:30 +0000
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Kees Cook <keescook@...omium.org>
Cc:     Christoph Hellwig <hch@....de>,
        WeiXiong Liao <gmpy.liaowx@...il.com>, axboe@...nel.dk,
        Anton Vorontsov <anton@...msg.org>,
        Colin Cross <ccross@...roid.com>,
        Tony Luck <tony.luck@...el.com>, linux-kernel@...r.kernel.org,
        linux-block@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] pstore/blk: Use the normal block device I/O path

On Mon, Jun 14, 2021 at 01:04:21PM -0700, Kees Cook wrote:
  
>  static ssize_t psblk_generic_blk_write(const char *buf, size_t bytes,
>  		loff_t pos)
>  {

>  	/* Console/Ftrace backend may handle buffer until flush dirty zones */
>  	if (in_interrupt() || irqs_disabled())
>  		return -EBUSY;

> +	return kernel_write(psblk_file, buf, bytes, &pos);

In which locking environments could that be called?  The checks above
look like that thing could be called from just about any context;
could that happen when the caller is holding a page locked?

IOW, what are those checks really trying to do?