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Subject[PATCH 2/3] lib, uaccess: add failure injection to usercopy functions
Date
From: Albert van der Linde <alinde@google.com>

To test fault-tolerance of usercopy accesses, introduce fault injection
in usercopy functions.

Adds failure injection to usercopy functions. If a failure is expected
we return either the failure or the total amount of bytes. As many
usercopy functions can fail partially, permit also partial failures:
e.g., copy_from_user can fail copying between 0 and n.

Signed-off-by: Albert van der Linde <alinde@google.com>
---
include/linux/uaccess.h | 31 ++++++++++++++++++++++++++-----
lib/iov_iter.c | 20 +++++++++++++++++---
lib/strncpy_from_user.c | 3 +++
lib/usercopy.c | 13 +++++++++++--
4 files changed, 57 insertions(+), 10 deletions(-)

diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index 94b285411659..79e736077ef4 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>
@@ -82,10 +83,14 @@ __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)
{
+ long not_copied = should_fail_usercopy(n);
+
+ if (not_copied < 0)
+ not_copied = n;
might_fault();
instrument_copy_from_user(to, from, n);
check_object_size(to, n, false);
- return raw_copy_from_user(to, from, n);
+ return not_copied + raw_copy_from_user(to, from, n - not_copied);
}

/**
@@ -104,18 +109,26 @@ __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)
{
+ long not_copied = should_fail_usercopy(n);
+
+ if (not_copied < 0)
+ not_copied = n;
instrument_copy_to_user(to, from, n);
check_object_size(from, n, true);
- return raw_copy_to_user(to, from, n);
+ return not_copied + raw_copy_to_user(to, from, n - not_copied);
}

static __always_inline __must_check unsigned long
__copy_to_user(void __user *to, const void *from, unsigned long n)
{
+ long not_copied = should_fail_usercopy(n);
+
+ if (not_copied < 0)
+ not_copied = n;
might_fault();
instrument_copy_to_user(to, from, n);
check_object_size(from, n, true);
- return raw_copy_to_user(to, from, n);
+ return not_copied + raw_copy_to_user(to, from, n - not_copied);
}

#ifdef INLINE_COPY_FROM_USER
@@ -123,10 +136,14 @@ static inline __must_check unsigned long
_copy_from_user(void *to, const void __user *from, unsigned long n)
{
unsigned long res = n;
+ long not_copied = should_fail_usercopy(n);
+
+ if (not_copied < 0)
+ not_copied = n;
might_fault();
if (likely(access_ok(from, n))) {
instrument_copy_from_user(to, from, n);
- res = raw_copy_from_user(to, from, n);
+ res = not_copied + raw_copy_from_user(to, from, n - not_copied);
}
if (unlikely(res))
memset(to + (n - res), 0, res);
@@ -141,10 +158,14 @@ _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)
{
+ long not_copied = should_fail_usercopy(n);
+
+ if (not_copied < 0)
+ not_copied = n;
might_fault();
if (access_ok(to, n)) {
instrument_copy_to_user(to, from, n);
- n = raw_copy_to_user(to, from, n);
+ n = not_copied + raw_copy_to_user(to, from, n - not_copied);
}
return n;
}
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 5e40786c8f12..c55c9bff9b0c 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>
@@ -139,18 +140,26 @@

static int copyout(void __user *to, const void *from, size_t n)
{
+ long not_copied = should_fail_usercopy(n);
+
+ if (not_copied < 0)
+ return not_copied;
if (access_ok(to, n)) {
instrument_copy_to_user(to, from, n);
- n = raw_copy_to_user(to, from, n);
+ n = not_copied + raw_copy_to_user(to, from, n - not_copied);
}
return n;
}

static int copyin(void *to, const void __user *from, size_t n)
{
+ long not_copied = should_fail_usercopy(n);
+
+ if (not_copied < 0)
+ return not_copied;
if (access_ok(from, n)) {
instrument_copy_from_user(to, from, n);
- n = raw_copy_from_user(to, from, n);
+ n = not_copied + raw_copy_from_user(to, from, n - not_copied);
}
return n;
}
@@ -640,9 +649,14 @@ EXPORT_SYMBOL(_copy_to_iter);
#ifdef CONFIG_ARCH_HAS_UACCESS_MCSAFE
static int copyout_mcsafe(void __user *to, const void *from, size_t n)
{
+ long not_copied = should_fail_usercopy(n);
+
+ if (not_copied < 0)
+ return not_copied;
if (access_ok(to, n)) {
instrument_copy_to_user(to, from, n);
- n = copy_to_user_mcsafe((__force void *) to, from, n);
+ n = not_copied + copy_to_user_mcsafe((__force void *) to,
+ from, n - not_copied);
}
return n;
}
diff --git a/lib/strncpy_from_user.c b/lib/strncpy_from_user.c
index 34696a348864..f65973007931 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>
@@ -101,6 +102,8 @@ long strncpy_from_user(char *dst, const char __user *src, long count)
might_fault();
if (unlikely(count <= 0))
return 0;
+ if (should_fail_usercopy(count))
+ return -EFAULT;

max_addr = user_addr_max();
src_addr = (unsigned long)untagged_addr(src);
diff --git a/lib/usercopy.c b/lib/usercopy.c
index b26509f112f9..e79716b4634b 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>

@@ -9,10 +10,14 @@
unsigned long _copy_from_user(void *to, const void __user *from, unsigned long n)
{
unsigned long res = n;
+ long not_copied = should_fail_usercopy(n);
+
+ if (not_copied < 0)
+ not_copied = n;
might_fault();
if (likely(access_ok(from, n))) {
instrument_copy_from_user(to, from, n);
- res = raw_copy_from_user(to, from, n);
+ res = not_copied + raw_copy_from_user(to, from, n - not_copied);
}
if (unlikely(res))
memset(to + (n - res), 0, res);
@@ -24,10 +29,14 @@ EXPORT_SYMBOL(_copy_from_user);
#ifndef INLINE_COPY_TO_USER
unsigned long _copy_to_user(void __user *to, const void *from, unsigned long n)
{
+ long not_copied = should_fail_usercopy(n);
+
+ if (not_copied < 0)
+ not_copied = n;
might_fault();
if (likely(access_ok(to, n))) {
instrument_copy_to_user(to, from, n);
- n = raw_copy_to_user(to, from, n);
+ n = not_copied + raw_copy_to_user(to, from, n - not_copied);
}
return n;
}
--
2.28.0.297.g1956fa8f8d-goog
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