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 1DF7E3BCD34 for ; Wed, 16 Sep 2026 16:07:07 +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=1789574828; cv=none; b=t3y11dCQa4NRD20eCCn9nWVV5XUFMyV6eCkQqDnT6ZsxkncKpPSVcdHomP/WChuKcrohQPRAcxA8EZs+Kz98/f6pWzPvzv9FGxiwQ4KiVgu2BcCkYROitbIVn05YC5jNm6GRbT3LiVB+Np5cjn/Yg/J9CIfoCXRngK9teYRS/Jw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789574828; c=relaxed/simple; bh=fi7bLisD2fTUze5Xemc0WwWqgp9VKXx8s+PGs02BBJ8=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=EF/JgMTBBrlS3m1wPm0ou3U1NqjPo+e7Xubu5a0fy/nyAi44r5/WQOtKopwPdfjtbChNf3bKkuKqJ6KoJ7zSqKR1ly3ph8NbxfloMbJQmfLEV6BRcQ4NFKHQgy6O/Yc5cOy2Z9EVVAHzBiePsdpDllt5gMEJ36MCWsr6Ma2aP60= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=v1267S/X; 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="v1267S/X" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 547C11F000FF; Wed, 16 Sep 2026 16:07:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789574826; bh=8dyrAO+H9QLIiaoNYTCgi69lMvOOHYyicrkvtpkn+Jw=; h=Subject:To:Cc:From:Date; b=v1267S/X2sFxVCa/xPcOQzIchku5F3/D3rj9Wb8FGJhUeNolgU1GDOBW4XEwIrgKq PKMaGSePVeImt3C2ymdVppEPEnceq7Hb8QP7JhqoOfVuH006dwA5lbS9L6q2vvcNtl 8NiuqzS0fCuTC+tbexHlLSIaFyIzfD6vXiB4JNK4= Subject: FAILED: patch "[PATCH] landlock: Fix use-after-free of the source's parent directory" failed to apply to 6.18-stable tree To: norbert@doyensec.com,gnoack3000@gmail.com,mic@digikod.net Cc: From: Date: Wed, 16 Sep 2026 16:46:39 +0100 Message-ID: <2026091639-trophy-refract-3155@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.18-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y git checkout FETCH_HEAD git cherry-pick -x 2c6dc792538260a8087ac5b22c31b3b8e47c85d6 # git commit -s git send-email --to '' --in-reply-to '2026091639-trophy-refract-3155@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..' Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 2c6dc792538260a8087ac5b22c31b3b8e47c85d6 Mon Sep 17 00:00:00 2001 From: Norbert Szetei Date: Sat, 22 Aug 2026 14:29:00 +0200 Subject: [PATCH] landlock: Fix use-after-free of the source's parent directory MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 diff --git a/security/landlock/fs.c b/security/landlock/fs.c index 30aa6ce13590..330a1871bf94 100644 --- a/security/landlock/fs.c +++ b/security/landlock/fs.c @@ -1298,11 +1298,12 @@ 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(subject->domain, mnt_dir.dentry, @@ -1311,8 +1312,10 @@ static int current_check_refer_path(struct dentry *const old_dentry, 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, @@ -1324,8 +1327,10 @@ static int current_check_refer_path(struct dentry *const old_dentry, 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; @@ -1335,6 +1340,7 @@ static int current_check_refer_path(struct dentry *const old_dentry, 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