Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   albert.linde@gmail.com
To:     akpm@linux-foundation.org, bp@alien8.de, mingo@redhat.com,
        corbet@lwn.net, tglx@linutronix.de, arnd@arndb.de
Cc:     akinobu.mita@gmail.com, hpa@zytor.com, viro@zeniv.linux.org.uk,
        glider@google.com, andreyknvl@google.com, dvyukov@google.com,
        elver@google.com, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
        x86@kernel.org, albert.linde@gmail.com,
        Albert van der Linde <alinde@google.com>
Subject: [PATCH v2 2/3] lib, uaccess: add failure injection to usercopy functions
Date:   Fri, 28 Aug 2020 14:13:43 +0000
Message-Id: <20200828141344.2277088-3-alinde@google.com>
In-Reply-To: <20200828141344.2277088-1-alinde@google.com>
References: <20200828141344.2277088-1-alinde@google.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

From: Albert van der Linde <alinde@google.com>

To test fault-tolerance of user memory access functions, introduce fault
injection to usercopy functions.

If a failure is expected return either -EFAULT or the total amount of
bytes that were not copied.

Signed-off-by: Albert van der Linde <alinde@google.com>
---
v2:
 - removed partial failures
---
 include/linux/uaccess.h | 11 ++++++++++-
 lib/iov_iter.c          |  5 +++++
 lib/strncpy_from_user.c |  3 +++
 lib/usercopy.c          |  5 ++++-
 4 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index 94b285411659..7fd54596af17 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -2,6 +2,7 @@
 #ifndef __LINUX_UACCESS_H__
 #define __LINUX_UACCESS_H__
 
+#include <linux/fault-inject-usercopy.h>
 #include <linux/instrumented.h>
 #include <linux/sched.h>
 #include <linux/thread_info.h>
@@ -82,6 +83,8 @@ __copy_from_user_inatomic(void *to, const void __user *from, unsigned long n)
 static __always_inline __must_check unsigned long
 __copy_from_user(void *to, const void __user *from, unsigned long n)
 {
+	if (should_fail_usercopy())
+		return n;
 	might_fault();
 	instrument_copy_from_user(to, from, n);
 	check_object_size(to, n, false);
@@ -104,6 +107,8 @@ __copy_from_user(void *to, const void __user *from, unsigned long n)
 static __always_inline __must_check unsigned long
 __copy_to_user_inatomic(void __user *to, const void *from, unsigned long n)
 {
+	if (should_fail_usercopy())
+		return n;
 	instrument_copy_to_user(to, from, n);
 	check_object_size(from, n, true);
 	return raw_copy_to_user(to, from, n);
@@ -112,6 +117,8 @@ __copy_to_user_inatomic(void __user *to, const void *from, unsigned long n)
 static __always_inline __must_check unsigned long
 __copy_to_user(void __user *to, const void *from, unsigned long n)
 {
+	if (should_fail_usercopy())
+		return n;
 	might_fault();
 	instrument_copy_to_user(to, from, n);
 	check_object_size(from, n, true);
@@ -124,7 +131,7 @@ _copy_from_user(void *to, const void __user *from, unsigned long n)
 {
 	unsigned long res = n;
 	might_fault();
-	if (likely(access_ok(from, n))) {
+	if (!should_fail_usercopy() && likely(access_ok(from, n))) {
 		instrument_copy_from_user(to, from, n);
 		res = raw_copy_from_user(to, from, n);
 	}
@@ -141,6 +148,8 @@ _copy_from_user(void *, const void __user *, unsigned long);
 static inline __must_check unsigned long
 _copy_to_user(void __user *to, const void *from, unsigned long n)
 {
+	if (should_fail_usercopy())
+		return n;
 	might_fault();
 	if (access_ok(to, n)) {
 		instrument_copy_to_user(to, from, n);
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 5e40786c8f12..eeac08855b24 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -2,6 +2,7 @@
 #include <crypto/hash.h>
 #include <linux/export.h>
 #include <linux/bvec.h>
+#include <linux/fault-inject-usercopy.h>
 #include <linux/uio.h>
 #include <linux/pagemap.h>
 #include <linux/slab.h>
@@ -139,6 +140,8 @@
 
 static int copyout(void __user *to, const void *from, size_t n)
 {
+	if (should_fail_usercopy())
+		return n;
 	if (access_ok(to, n)) {
 		instrument_copy_to_user(to, from, n);
 		n = raw_copy_to_user(to, from, n);
@@ -148,6 +151,8 @@ static int copyout(void __user *to, const void *from, size_t n)
 
 static int copyin(void *to, const void __user *from, size_t n)
 {
+	if (should_fail_usercopy())
+		return n;
 	if (access_ok(from, n)) {
 		instrument_copy_from_user(to, from, n);
 		n = raw_copy_from_user(to, from, n);
diff --git a/lib/strncpy_from_user.c b/lib/strncpy_from_user.c
index 34696a348864..eec7065e6342 100644
--- a/lib/strncpy_from_user.c
+++ b/lib/strncpy_from_user.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <linux/compiler.h>
 #include <linux/export.h>
+#include <linux/fault-inject-usercopy.h>
 #include <linux/kasan-checks.h>
 #include <linux/thread_info.h>
 #include <linux/uaccess.h>
@@ -98,6 +99,8 @@ long strncpy_from_user(char *dst, const char __user *src, long count)
 {
 	unsigned long max_addr, src_addr;
 
+	if (should_fail_usercopy())
+		return -EFAULT;
 	might_fault();
 	if (unlikely(count <= 0))
 		return 0;
diff --git a/lib/usercopy.c b/lib/usercopy.c
index b26509f112f9..766b6f8a6937 100644
--- a/lib/usercopy.c
+++ b/lib/usercopy.c
@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <linux/bitops.h>
+#include <linux/fault-inject-usercopy.h>
 #include <linux/instrumented.h>
 #include <linux/uaccess.h>
 
@@ -10,7 +11,7 @@ unsigned long _copy_from_user(void *to, const void __user *from, unsigned long n
 {
 	unsigned long res = n;
 	might_fault();
-	if (likely(access_ok(from, n))) {
+	if (!should_fail_usercopy() && likely(access_ok(from, n))) {
 		instrument_copy_from_user(to, from, n);
 		res = raw_copy_from_user(to, from, n);
 	}
@@ -24,6 +25,8 @@ EXPORT_SYMBOL(_copy_from_user);
 #ifndef INLINE_COPY_TO_USER
 unsigned long _copy_to_user(void __user *to, const void *from, unsigned long n)
 {
+	if (should_fail_usercopy())
+		return n;
 	might_fault();
 	if (likely(access_ok(to, n))) {
 		instrument_copy_to_user(to, from, n);
-- 
2.28.0.402.g5ffc5be6b7-goog