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 1A37E4E3254; Thu, 17 Sep 2026 15:53:01 +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=1789660382; cv=none; b=mJptcdu5f+kAiyFBqdY2iGrqxbiOA7+2wLfEhTR8/SUPNtFDYgUhY2GhOMxO8g/CmSq7hnjYVFiv1TyId76fmjGXDLjUZ3a83c9YIXbpZBblrt3FfzdkXrCPxXaa9wcnpGW1AaLIFO7qiHdpfwrF72rmU0/jLS+ZOaHHhxtc1jk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789660382; c=relaxed/simple; bh=FtEnFossfPEEaZJS0a3qXTrhkeAkih2BrP491459fO0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=dNU7mfc7bHl9LpA6/WFbRvxx2Z53qmtGR8vzSkQDLao86Pq7ZuzhJgNAT/rpktBgzqAIPic954Ti5zi2DKK1//jCYqRh+TO81hf1hXJxIut/+r4x7oRP0yrVK//Zbr9LS3s049NT8V4qqekR7wFROhBxPp9s9S00AC68qiisTlY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=w2ZzUqWQ; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="w2ZzUqWQ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 97E751F000FF; Thu, 17 Sep 2026 15:53:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789660381; bh=hwjK85WqO+mrXCIPmaXRLQJk3aI2Ba8ecOCV+43Usf0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=w2ZzUqWQS3iomVTvJArHWI/uAsXr7P8TyRh7NCiOKLga4zHsIZS3bdtcdvoeuzzBQ OaNIj0v7RNONbM+Ol5nz+NB+Ta2fgwfrKWqs+RsMW94c9elTX9xiXnxvIJp4YZF+1Z z8GMJVK2NAB5GUAvvTIAkBx9ViSDLm+XpK4vj7Lc= 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?= Subject: [PATCH 7.2 572/733] landlock: Fix use-after-free of the sources parent directory Date: Thu, 17 Sep 2026 16:14:40 +0100 Message-ID: <20260917151406.610551390@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260917151350.597953846@linuxfoundation.org> References: <20260917151350.597953846@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 7.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Norbert Szetei commit 2c6dc792538260a8087ac5b22c31b3b8e47c85d6 upstream. 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 Signed-off-by: Greg Kroah-Hartman --- security/landlock/fs.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) --- a/security/landlock/fs.c +++ b/security/landlock/fs.c @@ -1222,11 +1222,12 @@ static int current_check_refer_path(stru /* * 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(subject->domain, mnt_dir.dentry, @@ -1235,8 +1236,10 @@ static int current_check_refer_path(stru allow_parent2 = collect_domain_accesses(subject->domain, mnt_dir.dentry, new_dir->dentry, &layer_masks_parent2); - if (allow_parent1 && allow_parent2) + if (allow_parent1 && allow_parent2) { + dput(old_parent); return 0; + } /* * To be able to compare source and destination domain access rights, @@ -1248,8 +1251,10 @@ static int current_check_refer_path(stru subject->domain, &mnt_dir, access_request_parent1, &layer_masks_parent1, &request1, old_dentry, access_request_parent2, &layer_masks_parent2, &request2, - exchange ? new_dentry : NULL)) + exchange ? new_dentry : NULL)) { + dput(old_parent); return 0; + } if (request1.access) { request1.audit.u.path.dentry = old_parent; @@ -1259,6 +1264,7 @@ static int current_check_refer_path(stru request2.audit.u.path.dentry = new_dir->dentry; landlock_log_denial(subject, &request2); } + dput(old_parent); /* * This prioritizes EACCES over EXDEV for all actions, including