[156/156] lib, uaccess: add failure injection to usercopy functions

Commit Message

Andrew Morton Oct. 16, 2020, 2:50 a.m. UTC

From: Albert van der Linde <[e-mail]>
Subject: lib, uaccess: add failure injection to usercopy functions

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.

Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Albert van der Linde <[e-mail]>
Reviewed-by: Akinobu Mita <[e-mail]>
Reviewed-by: Alexander Potapenko <[e-mail]>
Cc: Al Viro <[e-mail]>
Cc: Andrey Konovalov <[e-mail]>
Cc: Arnd Bergmann <[e-mail]>
Cc: Borislav Petkov <[e-mail]>
Cc: Dmitry Vyukov <[e-mail]>
Cc: "H. Peter Anvin" <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Jonathan Corbet <[e-mail]>
Cc: Marco Elver <[e-mail]>
Cc: Peter Zijlstra (Intel) <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: Christoph Hellwig <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 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(-)

Patch

--- a/include/linux/uaccess.h~lib-uaccess-add-failure-injection-to-usercopy-functions
+++ a/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/minmax.h>
 #include <linux/sched.h>
@@ -84,6 +85,8 @@  static __always_inline __must_check unsi
 __copy_from_user(void *to, const void __user *from, unsigned long n)
 {
 	might_fault();
+	if (should_fail_usercopy())
+		return n;
 	instrument_copy_from_user(to, from, n);
 	check_object_size(to, n, false);
 	return raw_copy_from_user(to, from, n);
@@ -105,6 +108,8 @@  __copy_from_user(void *to, const void __
 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);
@@ -114,6 +119,8 @@  static __always_inline __must_check unsi
 __copy_to_user(void __user *to, const void *from, unsigned long n)
 {
 	might_fault();
+	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);
@@ -125,7 +132,7 @@  _copy_from_user(void *to, const void __u
 {
 	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);
 	}
@@ -143,6 +150,8 @@  static inline __must_check unsigned long
 _copy_to_user(void __user *to, const void *from, unsigned long n)
 {
 	might_fault();
+	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);
--- a/lib/iov_iter.c~lib-uaccess-add-failure-injection-to-usercopy-functions
+++ a/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>
@@ -140,6 +141,8 @@ 
 
 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);
@@ -149,6 +152,8 @@  static int copyout(void __user *to, cons
 
 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);
--- a/lib/strncpy_from_user.c~lib-uaccess-add-failure-injection-to-usercopy-functions
+++ a/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>
@@ -99,6 +100,8 @@  long strncpy_from_user(char *dst, const
 	unsigned long max_addr, src_addr;
 
 	might_fault();
+	if (should_fail_usercopy())
+		return -EFAULT;
 	if (unlikely(count <= 0))
 		return 0;
 
--- a/lib/usercopy.c~lib-uaccess-add-failure-injection-to-usercopy-functions
+++ a/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,
 {
 	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);
 	}
@@ -25,6 +26,8 @@  EXPORT_SYMBOL(_copy_from_user);
 unsigned long _copy_to_user(void __user *to, const void *from, unsigned long n)
 {
 	might_fault();
+	if (should_fail_usercopy())
+		return n;
 	if (likely(access_ok(to, n))) {
 		instrument_copy_to_user(to, from, n);
 		n = raw_copy_to_user(to, from, n);