From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D182178F2B for ; Thu, 14 Aug 2025 18:27:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755196021; cv=none; b=YK4t4QbU5fBaodOzDcOMkFjQmBaniesK0txaIsypDmKCaLnpR8CHaZ/yIV0ky+RHOGYwYlNskOzVU2nmyyM93RxHAfmf5R2w2jDlGnHE5ROMDNYcWcxUgHRYnOhCtzeZ+B9nxIPyvqZASyK5PikLSaq2aieJILghjyNPHQL9QeE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755196021; c=relaxed/simple; bh=JkBThSuYBCeGcbsIDoSX+/A/yMFC3KXC/p6bYfxrqXY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=XiCNXZQ6K0+zSRnoCP+DG/02G/Mw2rbtUzeSwwDMjI+5KqHg7utQowBnQ7jF4jgCr6c53L4mqzHQRULbVS/MjvXAw4KnyRaLNJgpJj+YHkD8rTCBG0nquTb0elSA1oCyLRcels1x8SGEGOE1jI021Hlo9iUVYgqrDL8LK98YxwI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=0OLUEc7Q; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="0OLUEc7Q" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BDAA1C4CEED; Thu, 14 Aug 2025 18:26:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1755196020; bh=JkBThSuYBCeGcbsIDoSX+/A/yMFC3KXC/p6bYfxrqXY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=0OLUEc7QHllhz5iPZJLWm4vZRLQNAcz6HJRsnkOG/Ebo3notX5y377B9xU1JSZifx fNnwiCKfBjPywXl7a+9ZodQRuygvFQP+J21Zu8/gvn60/3TOthAv192tQt+OhQ+p1a aRbuMOkmwuzTqbmS7DcbCDZqqnF511QSYDACyLbE= Date: Thu, 14 Aug 2025 20:26:56 +0200 From: Greg KH To: Benno Lossin Cc: Simona Vetter , Miguel Ojeda , Alex Gaynor , Boqun Feng , Gary Guo , =?iso-8859-1?Q?Bj=F6rn?= Roy Baron , Andreas Hindborg , Alice Ryhl , Trevor Gross , Danilo Krummrich , rust-for-linux@vger.kernel.org Subject: Re: [PATCH v4 0/4] Untrusted Data API Message-ID: <2025081435-broker-valium-7b22@gregkh> References: <20250814124424.516191-1-lossin@kernel.org> <2025081416-sufferer-economist-3f00@gregkh> <2025081448-creation-timid-b972@gregkh> Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Thu, Aug 14, 2025 at 07:23:45PM +0200, Benno Lossin wrote: > On Thu Aug 14, 2025 at 5:42 PM CEST, Greg KH wrote: > > On Thu, Aug 14, 2025 at 05:22:57PM +0200, Benno Lossin wrote: > >> On Thu Aug 14, 2025 at 4:37 PM CEST, Greg KH wrote: > >> > On Thu, Aug 14, 2025 at 02:44:12PM +0200, Benno Lossin wrote: > >> >> I didn't have too much time to spend on this API, so this is mostly a > >> >> resend of v3. There are some changes in the last commit, updating to the > >> >> latest version of Alice's iov_iter patche series [1] & rebasing on top > >> >> of v6.17-rc1. > >> >> > >> >> I think we should just merge the first two patches this cycle in order > >> >> to get the initial, bare-bones API into the kernel and have people > >> >> experiment with it. The validation logic in the third patch still needs > >> >> some work and I'd need to find some time to work on that (no idea when I > >> >> find it though). > >> > > >> > Nice, thanks for reviving this! > >> > > >> > And we should at least add an example using it, otherwise it's not going > >> > to help out much here. Add it to the misc device driver api? > >> > >> You mean `rust/kernel/miscdevice.rs`? What parts of that API are > >> untrusted? > > > > mmap() is, but you can't do anything about that... > > Which parameter is untrusted there and why can't I do anything about it? The whole memory range is untrusted as to what is written there, sorry, it was a bad attempt at a joke, the kernel never gets a chance to know what is happening. > > ioctl() is the callback that is taking untrusted data from userspace. > > That's one place we have had more kernel buffer overflows then I can > > count and ALWAYS needs to be properly verified before anything can be > > done with the data there. > > Are the `cmd` & `arg` parameters the untrusted part? Yes, especially as `arg` is usually a pointer to "something". > If so we probably > should have a single parameter so users can verify them at the same > time. Or am I thinking of the wrong thing to verify? (`file` should be > already in kernel memory, right?) Both are usually verified at different places, first `cmd` tells what `arg` is going to be, and then the code goes off and parses whatever `arg` points to (or contains for simple ioctls). And for some, `arg` is just a place to write something back, so `arg` needs no verification for them, it depends on what `cmd` is. thanks, greg k-h