From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5A7F0C43381 for ; Mon, 4 Mar 2019 08:35:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2382E20836 for ; Mon, 4 Mar 2019 08:35:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1551688541; bh=1TuZoTxiLcMNl0QECAeOBdZERSWJASN4Bpq+Dd6FpoQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=H0hPsGLkfCQUV8j7K7ysz6FKTE8E8d11WwQirGSPfZ45yMRRWnDyT1wS0jmcGI41/ hQ2e8lzGEfcPyagaYRZvnarjO+5dTrrp1TfZqRRZExEyRaP3IVlNCNdi1kS8taKp1F mMQyWHKFzGwBAUD+FQi7NUTt1mq7CXBkOWTw9wpA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728484AbfCDIfk (ORCPT ); Mon, 4 Mar 2019 03:35:40 -0500 Received: from mail.kernel.org ([198.145.29.99]:43876 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728252AbfCDIfh (ORCPT ); Mon, 4 Mar 2019 03:35:37 -0500 Received: from localhost (5356596B.cm-6-7b.dynamic.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 5668D20836; Mon, 4 Mar 2019 08:35:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1551688536; bh=1TuZoTxiLcMNl0QECAeOBdZERSWJASN4Bpq+Dd6FpoQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=G8WbsoAifYeBEgSqKqbAq1PTdDktzZm78juIItglQn1cYB0ArT0uFUmJ+ff8swJPp 7EtCJjzjRS4k53zVL8JML6F9Wxr5u2Kz62yWaM6PL6ey35AWli/bx5eJUR5tBTtY1C hO4JG4LXuHsaf7LSctHve+RcxRUQjmptfruo3Kgo= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, stable@kernel.org, Jann Horn , Linus Torvalds Subject: [PATCH 4.20 75/88] mm: enforce min addr even if capable() in expand_downwards() Date: Mon, 4 Mar 2019 09:22:58 +0100 Message-Id: <20190304081633.611254946@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190304081630.610632175@linuxfoundation.org> References: <20190304081630.610632175@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.20-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jann Horn commit 0a1d52994d440e21def1c2174932410b4f2a98a1 upstream. security_mmap_addr() does a capability check with current_cred(), but we can reach this code from contexts like a VFS write handler where current_cred() must not be used. This can be abused on systems without SMAP to make NULL pointer dereferences exploitable again. Fixes: 8869477a49c3 ("security: protect from stack expansion into low vm addresses") Cc: stable@kernel.org Signed-off-by: Jann Horn Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/mmap.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) --- a/mm/mmap.c +++ b/mm/mmap.c @@ -2415,12 +2415,11 @@ int expand_downwards(struct vm_area_stru { struct mm_struct *mm = vma->vm_mm; struct vm_area_struct *prev; - int error; + int error = 0; address &= PAGE_MASK; - error = security_mmap_addr(address); - if (error) - return error; + if (address < mmap_min_addr) + return -EPERM; /* Enforce stack_guard_gap */ prev = vma->vm_prev;