Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Tue, 5 May 2020 12:48:05 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Jann Horn <jannh@google.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Christoph Hellwig <hch@lst.de>, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        "Eric W . Biederman" <ebiederm@xmission.com>,
        Oleg Nesterov <oleg@redhat.com>,
        Russell King <linux@armlinux.org.uk>,
        linux-arm-kernel@lists.infradead.org,
        Mark Salter <msalter@redhat.com>,
        Aurelien Jacquiot <jacquiot.aurelien@gmail.com>,
        linux-c6x-dev@linux-c6x.org,
        Yoshinori Sato <ysato@users.sourceforge.jp>,
        Rich Felker <dalias@libc.org>, linux-sh@vger.kernel.org
Subject: Re: [PATCH v2 1/5] binfmt_elf_fdpic: Stop using dump_emit() on
 user pointers on !MMU
Message-ID: <20200505104805.GA17400@lst.de>
References: <20200429214954.44866-1-jannh@google.com> <20200429214954.44866-2-jannh@google.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20200429214954.44866-2-jannh@google.com>
User-Agent: Mutt/1.5.17 (2007-11-01)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Wed, Apr 29, 2020 at 11:49:50PM +0200, Jann Horn wrote:
> dump_emit() is for kernel pointers, and VMAs describe userspace memory.
> Let's be tidy here and avoid accessing userspace pointers under KERNEL_DS,
> even if it probably doesn't matter much on !MMU systems - especially given
> that it looks like we can just use the same get_dump_page() as on MMU if
> we move it out of the CONFIG_MMU block.

Looks sensible.  Did you get a chance to test this with a nommu setup?