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Date: Wed, 10 Jan 2018 18:02:36 -0800
From: Kees Cook <keescook@...omium.org>
To: linux-kernel@...r.kernel.org
Cc: Kees Cook <keescook@...omium.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	David Windsor <dave@...lcore.net>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andy Lutomirski <luto@...nel.org>,
	Christoph Hellwig <hch@...radead.org>,
	Christoph Lameter <cl@...ux.com>,
	"David S. Miller" <davem@...emloft.net>,
	Laura Abbott <labbott@...hat.com>,
	Mark Rutland <mark.rutland@....com>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Christian Borntraeger <borntraeger@...ibm.com>,
	Christoffer Dall <christoffer.dall@...aro.org>,
	Dave Kleikamp <dave.kleikamp@...cle.com>,
	Jan Kara <jack@...e.cz>,
	Luis de Bethencourt <luisbg@...nel.org>,
	Marc Zyngier <marc.zyngier@....com>,
	Rik van Riel <riel@...hat.com>,
	Matthew Garrett <mjg59@...gle.com>,
	linux-fsdevel@...r.kernel.org,
	linux-arch@...r.kernel.org,
	netdev@...r.kernel.org,
	linux-mm@...ck.org,
	kernel-hardening@...ts.openwall.com
Subject: [PATCH 04/38] lkdtm/usercopy: Adjust test to include an offset to check reporting

Instead of doubling the size, push the start position up by 16 bytes to
still trigger an overflow. This allows to verify that offset reporting
is working correctly.

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 drivers/misc/lkdtm_usercopy.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/misc/lkdtm_usercopy.c b/drivers/misc/lkdtm_usercopy.c
index a64372cc148d..9ebbb031e5e3 100644
--- a/drivers/misc/lkdtm_usercopy.c
+++ b/drivers/misc/lkdtm_usercopy.c
@@ -119,6 +119,8 @@ static void do_usercopy_heap_size(bool to_user)
 {
 	unsigned long user_addr;
 	unsigned char *one, *two;
+	void __user *test_user_addr;
+	void *test_kern_addr;
 	size_t size = unconst + 1024;
 
 	one = kmalloc(size, GFP_KERNEL);
@@ -139,27 +141,30 @@ static void do_usercopy_heap_size(bool to_user)
 	memset(one, 'A', size);
 	memset(two, 'B', size);
 
+	test_user_addr = (void __user *)(user_addr + 16);
+	test_kern_addr = one + 16;
+
 	if (to_user) {
 		pr_info("attempting good copy_to_user of correct size\n");
-		if (copy_to_user((void __user *)user_addr, one, size)) {
+		if (copy_to_user(test_user_addr, test_kern_addr, size / 2)) {
 			pr_warn("copy_to_user failed unexpectedly?!\n");
 			goto free_user;
 		}
 
 		pr_info("attempting bad copy_to_user of too large size\n");
-		if (copy_to_user((void __user *)user_addr, one, 2 * size)) {
+		if (copy_to_user(test_user_addr, test_kern_addr, size)) {
 			pr_warn("copy_to_user failed, but lacked Oops\n");
 			goto free_user;
 		}
 	} else {
 		pr_info("attempting good copy_from_user of correct size\n");
-		if (copy_from_user(one, (void __user *)user_addr, size)) {
+		if (copy_from_user(test_kern_addr, test_user_addr, size / 2)) {
 			pr_warn("copy_from_user failed unexpectedly?!\n");
 			goto free_user;
 		}
 
 		pr_info("attempting bad copy_from_user of too large size\n");
-		if (copy_from_user(one, (void __user *)user_addr, 2 * size)) {
+		if (copy_from_user(test_kern_addr, test_user_addr, size)) {
 			pr_warn("copy_from_user failed, but lacked Oops\n");
 			goto free_user;
 		}
-- 
2.7.4

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