[PATCH v2 05/11] arm64/uaccess: Enable hardened usercopy

Kees Cook
2016-07-13T21:57:21Z

Enables CONFIG_HARDENED_USERCOPY checks on arm64. As done by KASAN in -next,
renames the low-level functions to __arch_copy_*_user() so a static inline
can do additional work before the copy.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
arch/arm64/Kconfig | 2 ++
arch/arm64/include/asm/uaccess.h | 16 ++++++++++++++--
arch/arm64/kernel/arm64ksyms.c | 4 ++--
arch/arm64/lib/copy_from_user.S | 4 ++--
arch/arm64/lib/copy_to_user.S | 4 ++--
5 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 5a0a691d4220..b771cd97f74b 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -51,10 +51,12 @@ config ARM64
select HAVE_ALIGNED_STRUCT_PAGE if SLUB
select HAVE_ARCH_AUDITSYSCALL
select HAVE_ARCH_BITREVERSE
+ select HAVE_ARCH_HARDENED_USERCOPY
select HAVE_ARCH_HUGE_VMAP
select HAVE_ARCH_JUMP_LABEL
select HAVE_ARCH_KASAN if SPARSEMEM_VMEMMAP && !(ARM64_16K_PAGES && ARM64_VA_BITS_48)
select HAVE_ARCH_KGDB
+ select HAVE_ARCH_LINEAR_KERNEL_MAPPING
select HAVE_ARCH_MMAP_RND_BITS
select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT
select HAVE_ARCH_SECCOMP_FILTER
diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
index 9e397a542756..5d0dacdb695b 100644
--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h
@@ -256,11 +256,23 @@ do { \
-EFAULT; \
})

-extern unsigned long __must_check __copy_from_user(void *to, const void __user *from, unsigned long n);
-extern unsigned long __must_check __copy_to_user(void __user *to, const void *from, unsigned long n);
+extern unsigned long __must_check __arch_copy_from_user(void *to, const void __user *from, unsigned long n);
+extern unsigned long __must_check __arch_copy_to_user(void __user *to, const void *from, unsigned long n);
extern unsigned long __must_check __copy_in_user(void __user *to, const void __user *from, unsigned long n);
extern unsigned long __must_check __clear_user(void __user *addr, unsigned long n);

+static inline unsigned long __must_check __copy_from_user(void *to, const void __user *from, unsigned long n)
+{
+ check_object_size(to, n, false);
+ return __arch_copy_from_user(to, from, n);
+}
+
+static inline unsigned long __must_check __copy_to_user(void __user *to, const void *from, unsigned long n)
+{
+ check_object_size(from, n, true);
+ return __arch_copy_to_user(to, from, n);
+}
+
static inline unsigned long __must_check copy_from_user(void *to, const void __user *from, unsigned long n)
{
if (access_ok(VERIFY_READ, from, n))
diff --git a/arch/arm64/kernel/arm64ksyms.c b/arch/arm64/kernel/arm64ksyms.c
index 678f30b05a45..2dc44406a7ad 100644
--- a/arch/arm64/kernel/arm64ksyms.c
+++ b/arch/arm64/kernel/arm64ksyms.c
@@ -34,8 +34,8 @@ EXPORT_SYMBOL(copy_page);
EXPORT_SYMBOL(clear_page);

/* user mem (segment) */
-EXPORT_SYMBOL(__copy_from_user);
-EXPORT_SYMBOL(__copy_to_user);
+EXPORT_SYMBOL(__arch_copy_from_user);
+EXPORT_SYMBOL(__arch_copy_to_user);
EXPORT_SYMBOL(__clear_user);
EXPORT_SYMBOL(__copy_in_user);

diff --git a/arch/arm64/lib/copy_from_user.S b/arch/arm64/lib/copy_from_user.S
index 17e8306dca29..0b90497d4424 100644
--- a/arch/arm64/lib/copy_from_user.S
+++ b/arch/arm64/lib/copy_from_user.S
@@ -66,7 +66,7 @@
.endm

end .req x5
-ENTRY(__copy_from_user)
+ENTRY(__arch_copy_from_user)
ALTERNATIVE("nop", __stringify(SET_PSTATE_PAN(0)), ARM64_ALT_PAN_NOT_UAO, \
CONFIG_ARM64_PAN)
add end, x0, x2
@@ -75,7 +75,7 @@ ALTERNATIVE("nop", __stringify(SET_PSTATE_PAN(1)), ARM64_ALT_PAN_NOT_UAO, \
CONFIG_ARM64_PAN)
mov x0, #0 // Nothing to copy
ret
-ENDPROC(__copy_from_user)
+ENDPROC(__arch_copy_from_user)

.section .fixup,"ax"
.align 2
diff --git a/arch/arm64/lib/copy_to_user.S b/arch/arm64/lib/copy_to_user.S
index 21faae60f988..7a7efe255034 100644
--- a/arch/arm64/lib/copy_to_user.S
+++ b/arch/arm64/lib/copy_to_user.S
@@ -65,7 +65,7 @@
.endm

end .req x5
-ENTRY(__copy_to_user)
+ENTRY(__arch_copy_to_user)
ALTERNATIVE("nop", __stringify(SET_PSTATE_PAN(0)), ARM64_ALT_PAN_NOT_UAO, \
CONFIG_ARM64_PAN)
add end, x0, x2
@@ -74,7 +74,7 @@ ALTERNATIVE("nop", __stringify(SET_PSTATE_PAN(1)), ARM64_ALT_PAN_NOT_UAO, \
CONFIG_ARM64_PAN)
mov x0, #0
ret
-ENDPROC(__copy_to_user)
+ENDPROC(__arch_copy_to_user)

.section .fixup,"ax"
.align 2
--
2.7.4