From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 B51747083C; Wed, 22 Jul 2026 14:25:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784730345; cv=none; b=Zu7Q/N68c4VXgle83q5oyAuZzsgAAmlLdUulX1g5KwbIK9r6nhDB4J7Gmcc3xe6WlipODUNMa+By1WSqqOL/HR8bvi4OsEk949giMwjt4/+vECh07NyadZewoUzH+0JEQSAurYwhu4+cUpxRH0b3JE+v18sjR24FqR+u3S80828= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784730345; c=relaxed/simple; bh=x5OLo4YTWLIOMETrnu2IZQMFHkb9oKa0hKDXoZmkJ9E=; h=MIME-Version:Content-Type:Subject:From:To:Cc:In-Reply-To: References:Date:Message-Id; b=nhePJDHxXtLEoHDDmEBhL7piDO8AXjE8LUqHQccTH7jCph2RyQvsk++A9D0kEoW+eYR0pat+ZzOyuUhslzdTS7VFmzUExilrBEviZBvjQQV6aLiTkZdxxiZN6fNF77y4BX1GQKNym+jvBYb6AyKN3xVtG2uRoQHiIfRsqThQPSg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Mn9EOVCA; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Mn9EOVCA" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DD7811F000E9; Wed, 22 Jul 2026 14:25:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784730344; bh=MB2674Xq9iUX2pckuew3NqZMSr8/d8+HLDJJQm6Smho=; h=Subject:From:To:Cc:In-Reply-To:References:Date; b=Mn9EOVCAzHILrLnIRFbI/FT9YSc7lEimRoN2Rnq0bCq2CB3Yrm0nAh9KD7OaJc4K1 T0tQWhE6SUvOApZBKJWFs43mRBZjwJ3Y2DLVuAWnQTXZc1+Iywul5Ev4KBWBAifOi1 0hHakJMTDOL3wyN3EWuuKTN5FP7Ku5LcD12BR6/XAFkPIyQ76fZVdHX8h5Uv/EPREp nP8OcAOi+MFabL2DU3EKm7BnkHzDAWwEbzIAFMfoBQqrgV+qpFchIvJZTUtki/JmhY R4Y9kceUWZq3/Ax5d/LTt/hcrwujq7WFxEUTzufZEawYAppfHf8HRGH0RJR1FR0MEE iJLA2DJNSTYzQ== Precedence: bulk X-Mailing-List: linux-api@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Subject: Re: [RFC PATCH] fs: allow opening overlayfs/erofs layers through O_ALT From: Christian Brauner To: Miklos Szeredi Cc: Andy Lutomirski , Miklos Szeredi , Giuseppe Scrivano , linux-fsdevel@vger.kernel.org, linux-unionfs@vger.kernel.org, linux-api@vger.kernel.org, linux-erofs@lists.ozlabs.org, Amir Goldstein , Gao Xiang In-Reply-To: References: <20260715101107.973997-1-mszeredi@redhat.com> Date: Wed, 22 Jul 2026 16:25:39 +0200 Message-Id: <20260722-erraten-hinblick-erlesen-2520fd1a3726@brauner> X-Mailer: b4 0.16-dev-2f6f2 X-Developer-Signature: v=1; a=openpgp-sha256; l=774; i=brauner@kernel.org; h=from:subject:message-id; bh=x5OLo4YTWLIOMETrnu2IZQMFHkb9oKa0hKDXoZmkJ9E=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMWQlXHrqYplk+av8ybQPod1+C22T9/E9742v7JvsGnVaK PURn4djRykLgxgXg6yYIotDu0m43HKeis1GmRowc1iZQIYwcHEKwEQ4uRj+ys5333Noi32U0oyG 5vsm9q8NbiUeaol/ePmyQdo1/2XnGhj+B/HNPysa0Kf5RSChfwXXLIH951XVz28TjZ0VeCHy8ux d/AA= X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 On 2026-07-20 11:22 +0200, Miklos Szeredi wrote: > On Sun, 19 Jul 2026 at 16:13, Andy Lutomirski wrote: > > > This gives me the willies a bit. It's very cool, but it has some > > potential security issues that I think we need to watch out for. As > > sort-of prior art, NTFS supports alternate streams and Reiser4, ahem, > > supported files-as-directories. > > I realized that we can keep the creepiness factor minimal by > introducing this first in procfs only. That way zero changes are > needed in the path lookup code: > > sprintf(buf, "/proc/self/fd-alt/%d/%s", base_fd, alt_path); > alt_fd = open(buf, O_PATH); I'm still vehemently opposed to stuffing more creepy apis into procfs. So this gets clear opposition from me.