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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 71E00C43218 for ; Sat, 27 Apr 2019 15:25:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4DDF4206A3 for ; Sat, 27 Apr 2019 15:25:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728292AbfD0PZf (ORCPT ); Sat, 27 Apr 2019 11:25:35 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:33294 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727408AbfD0PPY (ORCPT ); Sat, 27 Apr 2019 11:15:24 -0400 Received: from [192.168.4.242] (helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1hKP2v-00014I-Id; Sat, 27 Apr 2019 16:15:21 +0100 Received: from ben by deadeye with local (Exim 4.92) (envelope-from ) id 1hKP2n-0004dl-OS; Sat, 27 Apr 2019 16:15:13 +0100 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, Denis Kirjanov , "Linus Torvalds" , "Jann Horn" Date: Sat, 27 Apr 2019 16:13:09 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) X-Patchwork-Hint: ignore Subject: [PATCH 3.16 181/202] mm: enforce min addr even if capable() in expand_downwards() In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.242 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.66-rc1 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") Signed-off-by: Jann Horn Signed-off-by: Linus Torvalds Signed-off-by: Ben Hutchings --- mm/mmap.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) --- a/mm/mmap.c +++ b/mm/mmap.c @@ -2244,12 +2244,11 @@ int expand_downwards(struct vm_area_stru unsigned long address) { 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;