From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757405AbaEPMxZ (ORCPT ); Fri, 16 May 2014 08:53:25 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:49565 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753680AbaEPMsV (ORCPT ); Fri, 16 May 2014 08:48:21 -0400 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, "Hugh Dickins" , "Dave Jones" , "Linus Torvalds" Date: Fri, 16 May 2014 13:47:21 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 19/34] mm: make fixup_user_fault() check the vma access rights too In-Reply-To: X-SA-Exim-Connect-IP: 2001:470:1f08:1539:3db0:c181:6526:5597 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 List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.59-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Linus Torvalds commit 1b17844b29ae042576bea588164f2f1e9590a8bc upstream. fixup_user_fault() is used by the futex code when the direct user access fails, and the futex code wants it to either map in the page in a usable form or return an error. It relied on handle_mm_fault() to map the page, and correctly checked the error return from that, but while that does map the page, it doesn't actually guarantee that the page will be mapped with sufficient permissions to be then accessed. So do the appropriate tests of the vma access rights by hand. [ Side note: arguably handle_mm_fault() could just do that itself, but we have traditionally done it in the caller, because some callers - notably get_user_pages() - have been able to access pages even when they are mapped with PROT_NONE. Maybe we should re-visit that design decision, but in the meantime this is the minimal patch. ] Found by Dave Jones running his trinity tool. Reported-by: Dave Jones Acked-by: Hugh Dickins Signed-off-by: Linus Torvalds Signed-off-by: Ben Hutchings --- mm/memory.c | 5 +++++ 1 file changed, 5 insertions(+) --- a/mm/memory.c +++ b/mm/memory.c @@ -1852,12 +1852,17 @@ int fixup_user_fault(struct task_struct unsigned long address, unsigned int fault_flags) { struct vm_area_struct *vma; + vm_flags_t vm_flags; int ret; vma = find_extend_vma(mm, address); if (!vma || address < vma->vm_start) return -EFAULT; + vm_flags = (fault_flags & FAULT_FLAG_WRITE) ? VM_WRITE : VM_READ; + if (!(vm_flags & vma->vm_flags)) + return -EFAULT; + ret = handle_mm_fault(mm, vma, address, fault_flags); if (ret & VM_FAULT_ERROR) { if (ret & VM_FAULT_OOM)