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 7991A563FBF; Wed, 9 Sep 2026 14:36:40 +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=1788964601; cv=none; b=ZRMGFQQS2Dl+7tFWQuIqUid1hFZTI/+b4gSD9XtoFaFDEIi6XOT5KHif5a6WSXKlyaW2pnNQBr1rTAJ0bHKobKrkkZxhJFhLt/B1cWnIS6RB4zQrOZyyxFJB7R46UHTrYOd+xoqB1w055L6p63sXJkX6tSX6pJeICXksx9J0sqI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788964601; c=relaxed/simple; bh=DD8+IZjLQDcaHRjirPyxy53K+p+TpS++td1QAofOvic=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=c1f3sDR6HkZczac23VSmd72sj43vY5qyX9VZirew+q9c0/8wnFkNLx9gkSdo8oJgaR62Cn8m/3f6Dvs+uHaaqf0peTukhiS/Nl0WcMSWGRfq+k3uQw783bmkXwhxrB/8gxq2uayOZAo7zXEeQrjzR/oCvJ5m9BNDSYZtL/ygWkc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=eFZFc1ue; 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="eFZFc1ue" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CA9731F00A3A; Wed, 9 Sep 2026 14:36:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788964600; bh=vRLi7LxoUtKX+3cC99ZymFi4xHtHlOK11QBbYZ6ewc4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=eFZFc1uep+r7ov4evvwT2usVMTCUR+ubQRO030IerWCHH/u5rgZ5hYhY33EpaFAyJ bfw7Gy9dASaWk+vZxkG3ik7gp5Zdo2hxGCB6l7XEwAASFObAZDL/rwsWfA/fs8iJI8 tHVOxdMgNk6Gcjrg+NydIVdSQPHlN8gfEyiEnMUw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Vivek Parikh , Amir Goldstein , "Christian Brauner (Amutable)" , Sasha Levin Subject: [PATCH 6.18 442/583] ovl: fix double end_creating() on the casefold-mismatch path Date: Wed, 9 Sep 2026 15:42:07 +0200 Message-ID: <20260909134253.293241200@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260909134237.773280130@linuxfoundation.org> References: <20260909134237.773280130@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-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Vivek Parikh [ Upstream commit 077ab8985ee278c3d8618182d335b0f0cd919e16 ] ovl_create_real() releases the new dentry twice when the casefold consistency check fails. The S_IFDIR branch calls end_creating() and sets err, then falls through to the common out: label which calls end_creating() on the same dentry again: case S_IFDIR: newdentry = ovl_do_mkdir(ofs, dir, newdentry, attr->mode); err = PTR_ERR_OR_ZERO(newdentry); if (!err && ofs->casefold != ovl_dentry_casefolded(newdentry)) { pr_warn_ratelimited(...); end_creating(newdentry); /* first */ err = -EINVAL; } break; ... if (err) goto out; ... out: if (err) { end_creating(newdentry); /* second, same dentry */ return ERR_PTR(err); } end_creating() is end_dirop(), which does inode_unlock() on the parent and dput() on the dentry, so the parent directory's i_rwsem is unlocked twice and the dentry is put twice. The second unlock releases a lock that is not held, which is what wedges every later creation under that parent, and the second dput() drops a reference that was never taken. The branch was added by commit dfc7da402ccc ("ovl: Check for casefold consistency when creating new dentries") as a bare dput(), which already released the reference twice; commit fe497f0759e0 ("VFS: change vfs_mkdir() to unlock on failure.") converted both sites to end_creating(), adding the double unlock. This is reachable by an unprivileged user. The casefold consistency of the layers is validated at mount time in ovl_parse_layer(), and again on every lookup in ovl_lookup_single(), but ofs->workdir is the internal "work" subdirectory created inside the user-supplied workdir, and that subdirectory is not re-checked. Marking it casefolded after the mount therefore makes every ovl_create_temp() inherit the wrong state - and that path reaches ovl_create_real() through ovl_start_creating_temp(), which uses start_creating() with a generated name and so never runs the lookup-time check. unshare -Urm mount -t tmpfs -o casefold=utf8-12.1.0 tmpfs mnt mkdir -p mnt/lower/d mnt/upper mnt/work mnt/merged mount -t overlay ovl -o lowerdir=mnt/lower,\ upperdir=mnt/upper,workdir=mnt/work mnt/merged chattr +F mnt/work/work mkdir mnt/merged/d/sub # directory copy-up overlayfs: wrong inherited casefold (work/#5) and the next copy-up blocks forever on the parent's i_rwsem: mkdir D start_creating+0x65/0xb0 ovl_start_creating_temp+0xb0/0xe0 [overlay] ovl_create_temp+0xa3/0x1d0 [overlay] ovl_copy_up_one+0x1f1c/0x21c0 [overlay] ovl_copy_up_flags+0xf5/0x140 [overlay] ovl_create_object+0xb7/0x220 [overlay] ovl_mkdir+0x23/0x40 [overlay] Drop the end_creating() from the branch and let out: own the cleanup, which is what every other error path in this function already does. Fixes: dfc7da402ccc ("ovl: Check for casefold consistency when creating new dentries") Cc: stable@vger.kernel.org Signed-off-by: Vivek Parikh Reviewed-by: Amir Goldstein Signed-off-by: Christian Brauner (Amutable) [ adapted end_creating() cleanup removal to the older dput() API ] Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- fs/overlayfs/dir.c | 1 - 1 file changed, 1 deletion(-) --- a/fs/overlayfs/dir.c +++ b/fs/overlayfs/dir.c @@ -191,7 +191,6 @@ struct dentry *ovl_create_real(struct ov if (!err && ofs->casefold != ovl_dentry_casefolded(newdentry)) { pr_warn_ratelimited("wrong inherited casefold (%pd2)\n", newdentry); - dput(newdentry); err = -EINVAL; } break;