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 2716F3FF8BE; Thu, 28 May 2026 18:26:14 +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=1779992776; cv=none; b=d5a3v9M2oCptGU50Sg+ZxNimKvx+sn6XM2SAtRNKC3KFBfGi4RGwiGn9Bu6AEwtwlmWjvZxyfS99iAujy7tu436Xs9sEze8VepHQFw8Nt/D1cWrQ+xORUzQtfFXDU8hsWcI5wbbcki9e411bD2wQG0GbNgeWjU0RBkSZKHIbsB4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779992776; c=relaxed/simple; bh=Jup5QZAB7CgZCOZgXzmqKuc+qMZisSNc6sUEIDv8XGM=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=Ij7C3mYo0qnjt7UW3YIDFN1jpHQFkCu9nO56wFBis/cqzuwByjWVF/9czmQ0O8roEjlEEr7xG3CNED638BhO49DpASDCHB1myLyd3GGC3KjAQMLzTko7BpcC7dDvqwlKJhUSsbj3HElEHXSbSHIW2hstjlC3dnDDciOhJdgUHk4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=DeTJ3VSw; 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="DeTJ3VSw" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D1B7E1F000E9; Thu, 28 May 2026 18:26:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1779992774; bh=umxsgUfAIAKmPR1v090QSLcMtlURT7J/ewk8HNWQtrk=; h=From:To:Cc:Subject:Date; b=DeTJ3VSwFKc3bt5yFdvGRk31HID8mMkQdxWCJdVMVIeLWNilaD/qsk9q89+RZd31Z pxBrqQWlZvMIDNIDJp9DZU2OH5zLRSmCXMCKYoDjuKTYWiwFcmIf5W8UWTuKNzv2RQ f8hcFCTnjezsMeRzp/GISxe1IFSfK8xtl8M9MRmRjRncmNuPOq09/pKeurdoH7C3aS RU2eeoJFhFeIzpbiiDrSrMGU0vuW+CQ80ObegYCTrdeanOQ6aihKpRSqYTicTfIYMl eEOK4q+h6efomljTBKF4j+v6J5/dXlLOKjryLlZdpNp/B6QmIcr0wg7Q6XwZKBow92 jcUR+9QNuNLAw== From: Song Liu To: linux-security-module@vger.kernel.org, linux-fsdevel@vger.kernel.org, selinux@vger.kernel.org, apparmor@lists.ubuntu.com Cc: paul@paul-moore.com, jmorris@namei.org, serge@hallyn.com, viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, john.johansen@canonical.com, stephen.smalley.work@gmail.com, omosnace@redhat.com, mic@digikod.net, gnoack@google.com, takedakn@nttdata.co.jp, penguin-kernel@I-love.SAKURA.ne.jp, herton@canonical.com, kernel-team@meta.com, Song Liu Subject: [PATCH v5 0/8] lsm: Replace security_sb_mount with granular mount hooks Date: Thu, 28 May 2026 11:25:59 -0700 Message-ID: <20260528182607.3150386-1-song@kernel.org> X-Mailer: git-send-email 2.52.0 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit This series replaces the monolithic security_sb_mount() hook with per-operation mount hooks, addressing two main issues: 1. TOCTOU: security_sb_mount() receives dev_name as a string, which LSMs like AppArmor and Tomoyo re-resolve via kern_path(). The new hooks pass pre-resolved struct path pointers where possible (bind mount, move mount), eliminating the double-resolution. 2. Conflation: security_sb_mount() handles bind, new mount, remount, move, propagation changes, and mount reconfiguration through a single hook, requiring LSMs to dispatch on flags internally. The new hooks are called at the operation level with appropriate context. The new hooks are: mount_bind - bind mount (pre-resolved source path) mount_new - new filesystem mount (with fs_context) mount_remount - filesystem remount (with fs_context) mount_reconfigure - mount flag reconfiguration (MS_REMOUNT|MS_BIND) mount_move - move mount (pre-resolved paths) mount_change_type - propagation type changes mount_new and mount_remount are called after parse_monolithic_mount_data(), so LSMs have access to the fs_context with parsed mount options. They also receive the original mount(2) flags and data pointer for LSMs (AppArmor, Tomoyo) that need them for policy matching. The series also replaces security_move_mount() with the new mount_move hook, unifying the old mount(2) MS_MOVE path with the move_mount(2) syscall path. All existing LSM behaviors are preserved: AppArmor: same policy matching, TOCTOU fixed for bind/move SELinux: same permission checks (FILE__MOUNTON, FILESYSTEM__REMOUNT) Landlock: same deny-all for sandboxed processes Tomoyo: same policy matching, TOCTOU fixed for bind/move, unused data_page parameter removed This work is inspired by earlier discussions: [1] https://lore.kernel.org/bpf/20251127005011.1872209-1-song@kernel.org/ [2] https://lore.kernel.org/linux-security-module/20250708230504.3994335-1-song@kernel.org/ Changes v4 => v5: 1. Restructure series: add new hooks in security/ first, then convert individual LSMs, then replace old hooks with new hooks in fs/namespace.c (single patch), then remove old hooks. This keeps all fs/namespace.c changes in one patch. (Christian Brauner) 2. Rebase. v4: https://lore.kernel.org/linux-security-module/20260515200158.4081915-1-song@kernel.org/ Changes v3 => v4: 1. Move LSM_HOOK_INIT(move_mount, ...) removal from patch 7/7 to each per-LSM conversion patch (3/7, 4/7, 5/7). (Paul Moore) 2. Add kdoc comments to tomoyo mount hook functions and rename tomoyo_move_mount to tomoyo_mount_move in patch 6/7. (Tetsuo Handa) 3. Add Acked-by from Tetsuo Handa to patch 6/7. v3: https://lore.kernel.org/linux-security-module/20260509015208.3853132-1-song@kernel.org/ Changes v2 => v3: 1. Rebase. 2. Move security_mount_move() call in vfs_move_mount() from patch 7/7 to patch 1/7. (Paul Moore) v2: https://lore.kernel.org/linux-security-module/20260430000315.918964-1-song@kernel.org/ Changes v1 => v2: 1. Rebase. 2. Add Reviewed-by and Tested-by from Stephen Smalley. v1: https://lore.kernel.org/linux-security-module/20260318184400.3502908-1-song@kernel.org/ Song Liu (8): lsm: Add granular mount hooks apparmor: Remove redundant MS_MGC_MSK stripping in apparmor_sb_mount apparmor: Convert from sb_mount to granular mount hooks selinux: Convert from sb_mount to granular mount hooks landlock: Convert from sb_mount to granular mount hooks tomoyo: Convert from sb_mount to granular mount hooks vfs: Replace security_sb_mount/security_move_mount with granular hooks lsm: Remove security_sb_mount and security_move_mount fs/namespace.c | 41 +++++++--- include/linux/lsm_hook_defs.h | 14 +++- include/linux/security.h | 56 +++++++++++--- kernel/bpf/bpf_lsm.c | 7 +- security/apparmor/include/mount.h | 5 +- security/apparmor/lsm.c | 102 ++++++++++++++++++------- security/apparmor/mount.c | 37 ++-------- security/landlock/fs.c | 41 ++++++++-- security/security.c | 119 +++++++++++++++++++++++------- security/selinux/hooks.c | 49 ++++++++---- security/tomoyo/common.h | 2 +- security/tomoyo/mount.c | 31 +++++--- security/tomoyo/tomoyo.c | 109 ++++++++++++++++++++++++--- 13 files changed, 457 insertions(+), 156 deletions(-) -- 2.53.0-Meta