linux-kernel - Re: [PATCH 05/13] fs: check FMODE_WRITE in __kernel

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Message-ID: <20200615123439.GT8681@bombadil.infradead.org>
Date:   Mon, 15 Jun 2020 05:34:39 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Christoph Hellwig <hch@....de>
Cc:     Al Viro <viro@...iv.linux.org.uk>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Ian Kent <raven@...maw.net>,
        David Howells <dhowells@...hat.com>,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        netfilter-devel@...r.kernel.org
Subject: Re: [PATCH 05/13] fs: check FMODE_WRITE in __kernel_write

On Mon, Jun 15, 2020 at 02:12:49PM +0200, Christoph Hellwig wrote:
> We still need to check if the fѕ is open write, even for the low-level
> helper.

Do we need the analogous check for FMODE_READ in the __kernel_read()
patch?

> @@ -505,6 +505,8 @@ ssize_t __kernel_write(struct file *file, const void *buf, size_t count, loff_t
>  	const char __user *p;
>  	ssize_t ret;
>  
> +	if (!(file->f_mode & FMODE_WRITE))
> +		return -EBADF;
>  	if (!(file->f_mode & FMODE_CAN_WRITE))
>  		return -EINVAL;
>  
> -- 
> 2.26.2
>