[PATCH v2 03/11] x86/uaccess: Enable hardened usercopy

Kees Cook
2016-07-13T21:56:46Z

Enables CONFIG_HARDENED_USERCOPY checks on x86. This is done both in
copy_*_user() and __copy_*_user() because copy_*_user() actually calls
down to _copy_*_user() and not __copy_*_user().

Based on code from PaX and grsecurity.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
arch/x86/Kconfig | 2 ++
arch/x86/include/asm/uaccess.h | 10 ++++++----
arch/x86/include/asm/uaccess_32.h | 2 ++
arch/x86/include/asm/uaccess_64.h | 2 ++
4 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 4407f596b72c..39d89e058249 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -80,11 +80,13 @@ config X86
select HAVE_ALIGNED_STRUCT_PAGE if SLUB
select HAVE_AOUT if X86_32
select HAVE_ARCH_AUDITSYSCALL
+ select HAVE_ARCH_HARDENED_USERCOPY
select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
select HAVE_ARCH_JUMP_LABEL
select HAVE_ARCH_KASAN if X86_64 && SPARSEMEM_VMEMMAP
select HAVE_ARCH_KGDB
select HAVE_ARCH_KMEMCHECK
+ select HAVE_ARCH_LINEAR_KERNEL_MAPPING if X86_64
select HAVE_ARCH_MMAP_RND_BITS if MMU
select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
select HAVE_ARCH_SECCOMP_FILTER
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index 2982387ba817..aa9cc58409c6 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -742,9 +742,10 @@ copy_from_user(void *to, const void __user *from, unsigned long n)
* case, and do only runtime checking for non-constant sizes.
*/

- if (likely(sz < 0 || sz >= n))
+ if (likely(sz < 0 || sz >= n)) {
+ check_object_size(to, n, false);
n = _copy_from_user(to, from, n);
- else if(__builtin_constant_p(n))
+ } else if(__builtin_constant_p(n))
copy_from_user_overflow();
else
__copy_from_user_overflow(sz, n);
@@ -762,9 +763,10 @@ copy_to_user(void __user *to, const void *from, unsigned long n)
might_fault();

/* See the comment in copy_from_user() above. */
- if (likely(sz < 0 || sz >= n))
+ if (likely(sz < 0 || sz >= n)) {
+ check_object_size(from, n, true);
n = _copy_to_user(to, from, n);
- else if(__builtin_constant_p(n))
+ } else if(__builtin_constant_p(n))
copy_to_user_overflow();
else
__copy_to_user_overflow(sz, n);
diff --git a/arch/x86/include/asm/uaccess_32.h b/arch/x86/include/asm/uaccess_32.h
index 4b32da24faaf..7d3bdd1ed697 100644
--- a/arch/x86/include/asm/uaccess_32.h
+++ b/arch/x86/include/asm/uaccess_32.h
@@ -37,6 +37,7 @@ unsigned long __must_check __copy_from_user_ll_nocache_nozero
static __always_inline unsigned long __must_check
__copy_to_user_inatomic(void __user *to, const void *from, unsigned long n)
{
+ check_object_size(from, n, true);
return __copy_to_user_ll(to, from, n);
}

@@ -95,6 +96,7 @@ static __always_inline unsigned long
__copy_from_user(void *to, const void __user *from, unsigned long n)
{
might_fault();
+ check_object_size(to, n, false);
if (__builtin_constant_p(n)) {
unsigned long ret;

diff --git a/arch/x86/include/asm/uaccess_64.h b/arch/x86/include/asm/uaccess_64.h
index 2eac2aa3e37f..673059a109fe 100644
--- a/arch/x86/include/asm/uaccess_64.h
+++ b/arch/x86/include/asm/uaccess_64.h
@@ -54,6 +54,7 @@ int __copy_from_user_nocheck(void *dst, const void __user *src, unsigned size)
{
int ret = 0;

+ check_object_size(dst, size, false);
if (!__builtin_constant_p(size))
return copy_user_generic(dst, (__force void *)src, size);
switch (size) {
@@ -119,6 +120,7 @@ int __copy_to_user_nocheck(void __user *dst, const void *src, unsigned size)
{
int ret = 0;

+ check_object_size(src, size, true);
if (!__builtin_constant_p(size))
return copy_user_generic((__force void *)dst, src, size);
switch (size) {
--
2.7.4