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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id h4-20020a17090a710400b0020ae09e9724sm474301pjk.53.2022.10.13.20.54.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 13 Oct 2022 20:54:15 -0700 (PDT) Date: Thu, 13 Oct 2022 20:54:14 -0700 From: Kees Cook To: Andy Lutomirski Cc: Jann Horn , Christian Brauner , "Eric W. Biederman" , Jorge Merlino , Al Viro , Thomas Gleixner , Sebastian Andrzej Siewior , Andrew Morton , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, John Johansen , Paul Moore , James Morris , "Serge E. Hallyn" , Stephen Smalley , Eric Paris , Richard Haines , Casey Schaufler , Xin Long , "David S. Miller" , Todd Kjos , Ondrej Mosnacek , Prashanth Prahlad , Micah Morton , Fenghua Yu , Andrei Vagin , Linux Kernel Mailing List , apparmor@lists.ubuntu.com, linux-security-module@vger.kernel.org, selinux@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH 1/2] fs/exec: Explicitly unshare fs_struct on exec Message-ID: <202210132052.32AE372@keescook> References: <20221006082735.1321612-1-keescook@chromium.org> <20221006082735.1321612-2-keescook@chromium.org> <20221006090506.paqjf537cox7lqrq@wittgenstein> <2032f766-1704-486b-8f24-a670c0b3cb32@app.fastmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2032f766-1704-486b-8f24-a670c0b3cb32@app.fastmail.com> ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1665719657; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=BQMeWu4NUS5XHxpYjKe5lPkeUdCMvZeCueelrFJNv7g=; b=1aQ+04RoaGz/ZZLwNaKOV735Qhbh8KIO2NxBx1oJmczRELyDAVwslqnjfDlfbhwX8rIx76 TXop7e0+fWnA/Gxv2rLUd/ZTD+Pb1G1ASiu/brc3k97Rx2IOHBuBfR0XiRTHzuDJC+2Li5 cSQbAf25/xS6QuCsALPoMuuA8IGfWN0= ARC-Authentication-Results: i=1; imf28.hostedemail.com; dkim=pass header.d=chromium.org header.s=google header.b=hVsj8yBr; spf=pass (imf28.hostedemail.com: domain of keescook@chromium.org designates 209.85.210.175 as permitted sender) smtp.mailfrom=keescook@chromium.org; dmarc=pass (policy=none) header.from=chromium.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1665719657; a=rsa-sha256; cv=none; b=zaz1c1Ok70RZE2kfP/MpuXXTB/wSJiCNGvte48+BYVHFSj2W5mOovovanH4+7BQLJO1wkz IFcMMHXZ2fz1XX6VeXmX5mX0J/KoQAIGjjUtfePaFLFejxMcMSDr+BgZmS9ZVWhkURFvbR DZWu63uOZveNUNUX6qLhU//6qWjstDU= X-Stat-Signature: 3dziutyypxj4g8ppg6yy46mnsmxgyo1o X-Rspamd-Queue-Id: 55D52C0025 Authentication-Results: imf28.hostedemail.com; dkim=pass header.d=chromium.org header.s=google header.b=hVsj8yBr; spf=pass (imf28.hostedemail.com: domain of keescook@chromium.org designates 209.85.210.175 as permitted sender) smtp.mailfrom=keescook@chromium.org; dmarc=pass (policy=none) header.from=chromium.org X-Rspam-User: X-Rspamd-Server: rspam09 X-HE-Tag: 1665719657-862326 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Oct 13, 2022 at 08:18:04PM -0700, Andy Lutomirski wrote: > But seriously, this makes no sense at all. It should not be possible to exec a program and then, without ptrace, change its cwd out from under it. Do we really need to preserve this behavior? Yup, already abandoned: https://lore.kernel.org/lkml/202210061301.207A20C8E5@keescook/ -- Kees Cook