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

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Message-ID: <CAHk-=whfMo7gvco8N5qEjh+jSqezv+bd+N-7txpNokD39t=dhQ@mail.gmail.com>
Date:   Mon, 15 Jun 2020 09:39:31 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Christoph Hellwig <hch@....de>
Cc:     Al Viro <viro@...iv.linux.org.uk>, Ian Kent <raven@...maw.net>,
        David Howells <dhowells@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        LSM List <linux-security-module@...r.kernel.org>,
        NetFilter <netfilter-devel@...r.kernel.org>
Subject: Re: [PATCH 05/13] fs: check FMODE_WRITE in __kernel_write

On Mon, Jun 15, 2020 at 5:13 AM Christoph Hellwig <hch@....de> wrote:
>
> We still need to check if the fѕ is open write, even for the low-level
> helper.

Is there actually a way to trigger something like this? I'm wondering
if it's worth a WARN_ON_ONCE()?

It doesn't sound sensible to have some kernel functionality try to
write to a file it didn't open for write, and sounds like a kernel bug
if this case were to ever trigger..

                Linus