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 5884638A72C; Wed, 17 Jun 2026 19:41:06 +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=1781725267; cv=none; b=qRCEhbSooP3fOk4C3peBqO7Zhp19I3ASHHcAr4WcIutkoM3w8XgfjqDzPOe6hMBFecZ8tnHh3emDQXQE8HFQ5/7A3S+Y6G8/1xAaRwbNX8QK8C0h+NVe312F09N+lqAdhzqhOrkFJUBG+UnysBFkLH3uctXzUy+DkWcMFuLnRzo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781725267; c=relaxed/simple; bh=cLCtUrFszsNpqaXSsFU9smSVm9I+BmoRFXf4J4vNNuw=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=QvIIzv9icA3xn0XOhTnpUDPvjJ6dBn1m1fLdUjLfRExlZblifb11CBLqM/p9FyqqXyZISbHCwmVIKwqH2uDO9eMeReqXYVbyKBTPgjesm4t3WGc/a/QjcpD2jNz5uM5DZLPwL+yjLsMYnYzQhJyILup073apFXRdqX08HUluJMw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=gWDvejAF; 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="gWDvejAF" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2BA611F000E9; Wed, 17 Jun 2026 19:41:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1781725266; bh=SOS1yGkhDPya+/uAhiZ1+Rq+6pspSgmQL30KoFCQaE4=; h=From:To:Cc:Subject:Date; b=gWDvejAFGLUPpouhULsa6FkMZlkYa1bbkiKWcOYyc6h8izFiTlHGQdTDxmdzm7Av6 6FVUbO3pIohmkRkC3dW+mxqY6hY5i0HYWosv43Bdh6bQx/0O8W9aEJir4BPzJ7nRW+ IKxlIkkG5tBeN6ghY8lO0i0Pn8ZnESPASKjFV0Tfrvx5V6bFxOuu+dY+d3olggfwNT a8Ukf+1UizEgbleF2FM7sVEu2QSSP5Cpws5MK2IYnhiO0azQ5Ao4zFECcrblB1SO7f 7NwIhJHk1LxugF7QS4kxIFPtZDvY6tftOGGZ4SrlSnBBabqHbZNpcJxpCwSuUjm7+K Wlxfi4YwIPNQQ== From: Mike Rapoport To: Andrew Morton , Linus Torvalds Cc: Alexander Viro , Christian Brauner , David Hildenbrand , Jan Kara , Mike Rapoport , Oleg Nesterov , Peter Xu , vova tokarev , linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org Subject: [PATCH] userfaultfd: prevent registration of special VMAs Date: Wed, 17 Jun 2026 22:40:59 +0300 Message-ID: <20260617194059.2529406-1-rppt@kernel.org> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: "Mike Rapoport (Microsoft)" Vova Tokarev says: userfaultfd allows registration on shadow stack VMAs. With userfaultfd access, you can register on the shadow stack, discard a page ... and inject a page with chosen return addresses via UFFDIO_COPY. Update vma_can_userfault() to reject VM_SHADOW_STACK. While on it, also reject VM_IO, VM_MIXEDMAP and VM_PFNMAP so that if a driver would implement vm_uffd_ops, it wouldn't be possible to register special VMAs with userfaultfd. Reported-by: vova tokarev Fixes: 54007f818206 ("mm: Introduce VM_SHADOW_STACK for shadow stack memory") Cc: Signed-off-by: Mike Rapoport (Microsoft) --- mm/userfaultfd.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 246af12bf801..b8d2d87ce8d7 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -2111,7 +2111,8 @@ static bool vma_can_userfault(struct vm_area_struct *vma, vm_flags_t vm_flags, { const struct vm_uffd_ops *ops = vma_uffd_ops(vma); - if (vma->vm_flags & VM_DROPPABLE) + if (vma->vm_flags & (VM_DROPPABLE | VM_IO | VM_MIXEDMAP | VM_PFNMAP | + VM_SHADOW_STACK)) return false; vm_flags &= __VM_UFFD_FLAGS; base-commit: e3d8707358ea76b78bdec9928937bb9a797f2c8f -- 2.53.0