From patchwork Tue Nov 15 10:59:19 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Michael Ellerman X-Patchwork-Id: 9430207 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 8990C60484 for ; Tue, 15 Nov 2016 16:46:40 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 7978828C2F for ; Tue, 15 Nov 2016 16:46:40 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 6C75228C31; Tue, 15 Nov 2016 16:46:40 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.2 required=2.0 tests=BAYES_00, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.wl.linuxfoundation.org (Postfix) with SMTP id 9868728C2F for ; Tue, 15 Nov 2016 16:46:39 +0000 (UTC) Received: (qmail 28266 invoked by uid 550); 15 Nov 2016 16:46:36 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Reply-To: kernel-hardening@lists.openwall.com Delivered-To: mailing list kernel-hardening@lists.openwall.com Delivered-To: moderator for kernel-hardening@lists.openwall.com Received: (qmail 7551 invoked from network); 15 Nov 2016 10:59:38 -0000 From: Michael Ellerman To: keescook@chromium.org Cc: kernel-hardening@lists.openwall.com, linux-kernel@vger.kernel.org Date: Tue, 15 Nov 2016 21:59:19 +1100 Message-Id: <1479207559-8510-1-git-send-email-mpe@ellerman.id.au> X-Mailer: git-send-email 2.7.4 Subject: [kernel-hardening] [PATCH] lkdtm: Add tests for LIST_POISON and ZERO_SIZE_PTR X-Virus-Scanned: ClamAV using ClamSMTP This adds two tests, to check that a read or write to LIST_POISON1 and ZERO_SIZE_PTR are blocked. The default values for both (256 and 16) typically fall in the range of valid user space addresses. However in general mmap_min_addr is 64K, which prevents user space from mapping anything at those addresses. However it's feasible that an attacker will be able to find a way to cause an access at an offset from either value, and if that offset is greater than 64K then they can access user space again. To simulate that case, in the test we create a user mapping at mmap_min_addr, and offset the pointer by that amount. This gives the test the greatest chance of failing (ie. an access succeeding). Signed-off-by: Michael Ellerman --- drivers/misc/lkdtm.h | 2 ++ drivers/misc/lkdtm_bugs.c | 44 ++++++++++++++++++++++++++++++++++++++++++++ drivers/misc/lkdtm_core.c | 2 ++ 3 files changed, 48 insertions(+) diff --git a/drivers/misc/lkdtm.h b/drivers/misc/lkdtm.h index fdf954c2107f..cc207f7824f9 100644 --- a/drivers/misc/lkdtm.h +++ b/drivers/misc/lkdtm.h @@ -21,6 +21,8 @@ void lkdtm_SPINLOCKUP(void); void lkdtm_HUNG_TASK(void); void lkdtm_ATOMIC_UNDERFLOW(void); void lkdtm_ATOMIC_OVERFLOW(void); +void lkdtm_ACCESS_LIST_POISON(void); +void lkdtm_ACCESS_ZERO_SIZE_PTR(void); /* lkdtm_heap.c */ void lkdtm_OVERWRITE_ALLOCATION(void); diff --git a/drivers/misc/lkdtm_bugs.c b/drivers/misc/lkdtm_bugs.c index 182ae1894b32..35ce9c753b48 100644 --- a/drivers/misc/lkdtm_bugs.c +++ b/drivers/misc/lkdtm_bugs.c @@ -5,7 +5,10 @@ * test source files. */ #include "lkdtm.h" +#include #include +#include +#include /* * Make sure our attempts to over run the kernel stack doesn't trigger @@ -146,3 +149,44 @@ void lkdtm_ATOMIC_OVERFLOW(void) pr_info("attempting bad atomic overflow\n"); atomic_inc(&over); } + +static void test_poison_ptr(void *base, const char *desc) +{ + unsigned long *ptr, val, uaddr; + + uaddr = vm_mmap(NULL, mmap_min_addr, PAGE_SIZE, PROT_READ | PROT_WRITE, + MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED, 0); + if (uaddr >= TASK_SIZE) { + pr_warn("Failed to allocate user memory, can't perform test.\n"); + return; + } + + /* + * Creating a mapping and adding mmap_min_addr to the value is cheating + * in a way. But it simulates the case where an attacker is able to + * cause an access at a small offset from the base value, leading to a + * user space access. If an arch doesn't define CONFIG_ILLEGAL_POINTER_VALUE + * then it's likely this will work in the absence of other protections. + */ + ptr = mmap_min_addr + base; + + pr_info("attempting read of %s %p\n", desc, ptr); + val = *ptr; + pr_info("FAIL: Was able to read %s! Got 0x%lx\n", desc, val); + + pr_info("attempting write of %s %p\n", desc, ptr); + *ptr = 0xdeadbeefabcd1234; + pr_info("FAIL: Was able to write %s! Now = 0x%lx\n", desc, *ptr); + + vm_munmap(uaddr, PAGE_SIZE); +} + +void lkdtm_ACCESS_LIST_POISON(void) +{ + test_poison_ptr(LIST_POISON1, "LIST_POISON"); +} + +void lkdtm_ACCESS_ZERO_SIZE_PTR(void) +{ + test_poison_ptr(ZERO_SIZE_PTR, "ZERO_SIZE_PTR"); +} diff --git a/drivers/misc/lkdtm_core.c b/drivers/misc/lkdtm_core.c index f9154b8d67f6..025a0ee8d8ee 100644 --- a/drivers/misc/lkdtm_core.c +++ b/drivers/misc/lkdtm_core.c @@ -220,6 +220,8 @@ struct crashtype crashtypes[] = { CRASHTYPE(WRITE_KERN), CRASHTYPE(ATOMIC_UNDERFLOW), CRASHTYPE(ATOMIC_OVERFLOW), + CRASHTYPE(ACCESS_LIST_POISON), + CRASHTYPE(ACCESS_ZERO_SIZE_PTR), CRASHTYPE(USERCOPY_HEAP_SIZE_TO), CRASHTYPE(USERCOPY_HEAP_SIZE_FROM), CRASHTYPE(USERCOPY_HEAP_FLAG_TO),