From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f202.google.com ([209.85.220.202]:42381 "EHLO mail-qk0-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727453AbeH2AIR (ORCPT ); Tue, 28 Aug 2018 20:08:17 -0400 Received: by mail-qk0-f202.google.com with SMTP id z17-v6so2367896qka.9 for ; Tue, 28 Aug 2018 13:15:02 -0700 (PDT) Date: Tue, 28 Aug 2018 22:14:21 +0200 In-Reply-To: <20180828201421.157735-1-jannh@google.com> Message-Id: <20180828201421.157735-8-jannh@google.com> Mime-Version: 1.0 References: <20180828201421.157735-1-jannh@google.com> Subject: [PATCH v3 7/7] lkdtm: test copy_to_user() on bad kernel pointer under KERNEL_DS From: Jann Horn To: Kees Cook , Thomas Gleixner , Ingo Molnar , x86@kernel.org, Andy Lutomirski , kernel-hardening@lists.openwall.com, jannh@google.com Cc: linux-kernel@vger.kernel.org, dvyukov@google.com, Masami Hiramatsu , "Naveen N. Rao" , Anil S Keshavamurthy , "David S. Miller" , Alexander Viro , linux-fsdevel@vger.kernel.org, Borislav Petkov Content-Type: text/plain; charset="UTF-8" Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Test whether the kernel WARN()s when, under KERNEL_DS, a bad kernel pointer is used as "userspace" pointer. Should normally be used in "DIRECT" mode. Acked-by: Kees Cook Signed-off-by: Jann Horn --- drivers/misc/lkdtm/core.c | 1 + drivers/misc/lkdtm/lkdtm.h | 1 + drivers/misc/lkdtm/usercopy.c | 13 +++++++++++++ 3 files changed, 15 insertions(+) diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c index 2154d1bfd18b..5a755590d3dc 100644 --- a/drivers/misc/lkdtm/core.c +++ b/drivers/misc/lkdtm/core.c @@ -183,6 +183,7 @@ static const struct crashtype crashtypes[] = { CRASHTYPE(USERCOPY_STACK_FRAME_FROM), CRASHTYPE(USERCOPY_STACK_BEYOND), CRASHTYPE(USERCOPY_KERNEL), + CRASHTYPE(USERCOPY_KERNEL_DS), }; diff --git a/drivers/misc/lkdtm/lkdtm.h b/drivers/misc/lkdtm/lkdtm.h index 9e513dcfd809..07db641d71d0 100644 --- a/drivers/misc/lkdtm/lkdtm.h +++ b/drivers/misc/lkdtm/lkdtm.h @@ -82,5 +82,6 @@ void lkdtm_USERCOPY_STACK_FRAME_TO(void); void lkdtm_USERCOPY_STACK_FRAME_FROM(void); void lkdtm_USERCOPY_STACK_BEYOND(void); void lkdtm_USERCOPY_KERNEL(void); +void lkdtm_USERCOPY_KERNEL_DS(void); #endif diff --git a/drivers/misc/lkdtm/usercopy.c b/drivers/misc/lkdtm/usercopy.c index 9725aed305bb..389475b25bb7 100644 --- a/drivers/misc/lkdtm/usercopy.c +++ b/drivers/misc/lkdtm/usercopy.c @@ -322,6 +322,19 @@ void lkdtm_USERCOPY_KERNEL(void) vm_munmap(user_addr, PAGE_SIZE); } +void lkdtm_USERCOPY_KERNEL_DS(void) +{ + char __user *user_ptr = (char __user *)ERR_PTR(-EINVAL); + mm_segment_t old_fs = get_fs(); + char buf[10] = {0}; + + pr_info("attempting copy_to_user on unmapped kernel address\n"); + set_fs(KERNEL_DS); + if (copy_to_user(user_ptr, buf, sizeof(buf))) + pr_info("copy_to_user un unmapped kernel address failed\n"); + set_fs(old_fs); +} + void __init lkdtm_usercopy_init(void) { /* Prepare cache that lacks SLAB_USERCOPY flag. */ -- 2.19.0.rc0.228.g281dcd1b4d0-goog