From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793212132; b=e5evuLndxo9Iz+4jnNpra3R/DS48mMSkD0UTg0BKb9MX7Frhm3zGByXy+iWdakNcs3mu 3fir/0tDWdoypec7RJkYNEvNY6jfLQPITaZQNY7uwtl6jS4Y8Pr68UJPgT10suVBfIgRv QIMUeVMyee2ccI4rZlMOq0fFVXDkCOcYrmR5lIRU860joFDVdhKfLaqZCp8cPP2JWyMOq QoyhyjRaq4U4oj6jilpO/KdlMffQWbuajycLYXmSxkLv9Ua074D991aX1KWT1XV1bbueW hJntc8IPxeLLQ1eBHuAvB7ZuDeVZ6IZHNOLOCj2asgJ9mfQ9jnR66mUlxUknT/mT5lg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793212132; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=TJUf1nVEaUlTLZPaIBMLu7kgrx/VjviT21//ouNrMjQ=; b=wZLa6BH26x802xQ0V+DkONEtThRb/2LUingq1HWmBO1rGw8buWLLO0zwDXimP2ytpKNG tlgeob2y0cDQvWXARI91WH5Rv12Yg8hrzG5BUB1ogr8JwkH47kpzE7IX5yxYZ2Ibzukoi bJ1zDokJDecaHTVf9s+ZbAvb+Uld9PD/QLbfiFtvxz2pLv5Qb5J44t8j053fr17qTeDFv hGlGMRktd99DcBjc/2pIUfpgqs9NB6lPQDP+UvMnaMl9vnXnkltuaDZ8sEIwIYthfy73f vX2bxMUWhuFvlluJ5Rr6/aVpd0rweyqLQEDxHk0jsCso7sKt2cV8MlZTszOh/hnb5Qw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=VJo4Gf2L; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A0489606A31D; Wed, 28 Oct 2026 18:28:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=VJo4Gf2L Received: by smtp.kernel.org (Postfix) with ESMTPSA id F1EBC1F01825; Wed, 28 Oct 2026 18:28:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793212132; bh=TJUf1nVEaUlTLZPaIBMLu7kgrx/VjviT21//ouNrMjQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=VJo4Gf2LD7xmopVBkWpE/9zD+ggrfOb1wM7wV0Q2lzKj6SBYHLkhlGrZ6T2QvkqHt 6Pr3k676JCuBolXzRk0PsT8aVJBeu94XEI5pIFjQppMG413g2aFOx4/Df94ulLnWjI 25BSihhcct5dFOci0tfSjXkjiNgEFuo7VmJxCRlg= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Norbert Szetei , =?UTF-8?q?G=C3=BCnther=20Noack?= , =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= , Sasha Levin Subject: [PATCH 6.1 0048/1887] landlock: Fix use-after-free of the sources parent directory Date: Wed, 28 Oct 2026 17:35:44 +0100 Message-ID: <20261028170500.320445882@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261028170459.200466217@linuxfoundation.org> References: <20261028170459.200466217@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Norbert Szetei [ Upstream commit 2c6dc792538260a8087ac5b22c31b3b8e47c85d6 ] current_check_refer_path() reads old_dentry->d_parent without holding a reference nor a lock on it, and then dereferences it in collect_domain_accesses() and in the audit record. A reference on a child does not pin its parent: __d_move() reassigns dentry->d_parent and drops the reference the child held on its former parent. hook_path_rename() is not affected because the rename path calls lock_rename() before the hook, so the source cannot be reparented under it. hook_path_link() has no such protection: filename_linkat() holds a reference on the source dentry but neither locks nor references its parent, so a concurrent rename(2) can reparent the source while security_path_link() runs, and the former parent can then be removed and freed while the hook walks it. A process can trigger this after entering a Landlock domain that handles at least one filesystem access right. The process can then race a linkat(2) loop against rename(2) and rmdir(2): BUG: KASAN: slab-use-after-free in collect_domain_accesses+0x278/0x290 Read of size 4 at addr ffff888160bd53f4 by task llrepro2/549 collect_domain_accesses+0x278/0x290 current_check_refer_path+0x952/0x1120 security_path_link+0x1be/0x320 filename_linkat+0x342/0x6d0 __x64_sys_linkat+0xfa/0x150 Freed by task 562: kmem_cache_free+0x139/0x4c0 i_callback+0x4b/0x80 rcu_core+0x7dc/0x10a0 Take a reference on the dentry selected as the source parent, using dget() for the common-mount-root case and dget_parent() otherwise. Release it after the hierarchy walk and synchronous audit logging. Cc: stable@vger.kernel.org Fixes: b91c3e4ea756 ("landlock: Add support for file reparenting with LANDLOCK_ACCESS_FS_REFER") Signed-off-by: Norbert Szetei Reviewed-by: Günther Noack Tested-by: Günther Noack Link: https://patch.msgid.link/E9CDD9E6-E960-4DE2-B1AC-5667D52ABB3E@doyensec.com [mic: Clarify the caller, reachability, and reference handling] Signed-off-by: Mickaël Salaün [ consolidated dput(old_parent) into one release after the hierarchy walks because the older branch lacks audit logging. ] Signed-off-by: Sasha Levin --- security/landlock/fs.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/security/landlock/fs.c b/security/landlock/fs.c index 8f20a146648cf..4e03da721e633 100644 --- a/security/landlock/fs.c +++ b/security/landlock/fs.c @@ -911,17 +911,19 @@ static int current_check_refer_path(struct dentry *const old_dentry, /* * old_dentry may be the root of the common mount point and * !IS_ROOT(old_dentry) at the same time (e.g. with open_tree() and - * OPEN_TREE_CLONE). We do not need to call dget(old_parent) because - * we keep a reference to old_dentry. + * OPEN_TREE_CLONE). Pin the dentry used as old_parent in either case. + * Otherwise, dget_parent() safely fetches and pins the current parent + * against a concurrent rename(2). */ - old_parent = (old_dentry == mnt_dir.dentry) ? old_dentry : - old_dentry->d_parent; + old_parent = (old_dentry == mnt_dir.dentry) ? dget(old_dentry) : + dget_parent(old_dentry); /* new_dir->dentry is equal to new_dentry->d_parent */ allow_parent1 = collect_domain_accesses(dom, mnt_dir.dentry, old_parent, &layer_masks_parent1); allow_parent2 = collect_domain_accesses( dom, mnt_dir.dentry, new_dir->dentry, &layer_masks_parent2); + dput(old_parent); if (allow_parent1 && allow_parent2) return 0; -- 2.53.0