From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from second.openwall.net (second.openwall.net [193.110.157.125]) by smtp.lore.kernel.org (Postfix) with SMTP id 83FCEC3DA4B for ; Wed, 17 Jul 2024 13:04:17 +0000 (UTC) Received: (qmail 12134 invoked by uid 550); 17 Jul 2024 12:59:02 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Received: (qmail 22259 invoked from network); 17 Jul 2024 08:26:33 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=python.org; s=200901; t=1721204783; bh=fTteDRfXe9Vlvc3/MVkCR1QexOCfXk5wsr0WUqhKjwI=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=hYt2BvmbQYJcbMIPmDyPk0v5DDLpQwvR7wOKYjhJ3uw3TuQItzbBjTZiqlNAJKVbP 7sccz+rS3ckrUp0F+K65M4OQN+VxdVTR8jl+PZ319XHPjr0ZHkx3SGkX0fwY3O6JrT Bb0ws6UinibHmFcuTiPzn/7nhblRN247FK4zx72Y= Message-ID: Date: Wed, 17 Jul 2024 09:26:22 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH v19 1/5] exec: Add a new AT_CHECK flag to execveat(2) Content-Language: en-GB To: Jeff Xu , =?UTF-8?Q?Micka=C3=ABl_Sala=C3=BCn?= Cc: Al Viro , Christian Brauner , Kees Cook , Linus Torvalds , Paul Moore , Theodore Ts'o , Alejandro Colomar , Aleksa Sarai , Andrew Morton , Andy Lutomirski , Arnd Bergmann , Casey Schaufler , Christian Heimes , Dmitry Vyukov , Eric Biggers , Eric Chiang , Fan Wu , Florian Weimer , Geert Uytterhoeven , James Morris , Jan Kara , Jann Horn , Jonathan Corbet , Jordan R Abrahams , Lakshmi Ramasubramanian , Luca Boccassi , Luis Chamberlain , "Madhavan T . Venkataraman" , Matt Bobrowski , Matthew Garrett , Matthew Wilcox , Miklos Szeredi , Mimi Zohar , Nicolas Bouchinet , Scott Shell , Shuah Khan , Stephen Rothwell , Steve Grubb , Thibaut Sautereau , Vincent Strubel , Xiaoming Ni , Yin Fengwei , kernel-hardening@lists.openwall.com, linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org References: <20240704190137.696169-1-mic@digikod.net> <20240704190137.696169-2-mic@digikod.net> From: Steve Dower In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 17/07/2024 07:33, Jeff Xu wrote: > Consider those cases: I think: > a> relying purely on userspace for enforcement does't seem to be > effective, e.g. it is trivial to call open(), then mmap() it into > executable memory. If there's a way to do this without running executable code that had to pass a previous execveat() check, then yeah, it's not effective (e.g. a Python interpreter that *doesn't* enforce execveat() is a trivial way to do it). Once arbitrary code is running, all bets are off. So long as all arbitrary code is being checked itself, it's allowed to do things that would bypass later checks (and it's up to whoever audited it in the first place to prevent this by not giving it the special mark that allows it to pass the check). > b> if both user space and kernel need to call AT_CHECK, the faccessat > seems to be a better place for AT_CHECK, e.g. kernel can call > do_faccessat(AT_CHECK) and userspace can call faccessat(). This will > avoid complicating the execveat() code path. > > What do you think ? > > Thanks > -Jeff