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Date: Wed, 15 Feb 2017 12:05:57 -0800
From: Kees Cook <keescook@...omium.org>
To: Russell King <linux@...linux.org.uk>
Cc: Mark Rutland <mark.rutland@....com>, Al Viro <viro@...iv.linux.org.uk>,
Robin Murphy <robin.murphy@....com>, linux-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org,
kernel-hardening@...ts.openwall.com
Subject: [PATCH] ARM: uaccess: consistently check object sizes
In commit 76624175dcae ("arm64: uaccess: consistently check object sizes"),
the object size checks are moved outside the access_ok() so that bad
destinations are detected before hitting the "memset(dest, 0, size)" in the
copy_from_user() failure path.
This makes the same change for arm, with attention given to possibly
extracting the uaccess routines into a common header file for all
architectures in the future.
Suggested-by: Mark Rutland <mark.rutland@....com>
Signed-off-by: Kees Cook <keescook@...omium.org>
---
arch/arm/include/asm/uaccess.h | 44 ++++++++++++++++++++++++++++++------------
1 file changed, 32 insertions(+), 12 deletions(-)
diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h
index 1f59ea051bab..b7e0125c0bbf 100644
--- a/arch/arm/include/asm/uaccess.h
+++ b/arch/arm/include/asm/uaccess.h
@@ -478,11 +478,10 @@ extern unsigned long __must_check
arm_copy_from_user(void *to, const void __user *from, unsigned long n);
static inline unsigned long __must_check
-__copy_from_user(void *to, const void __user *from, unsigned long n)
+__arch_copy_from_user(void *to, const void __user *from, unsigned long n)
{
unsigned int __ua_flags;
- check_object_size(to, n, false);
__ua_flags = uaccess_save_and_enable();
n = arm_copy_from_user(to, from, n);
uaccess_restore(__ua_flags);
@@ -495,18 +494,15 @@ extern unsigned long __must_check
__copy_to_user_std(void __user *to, const void *from, unsigned long n);
static inline unsigned long __must_check
-__copy_to_user(void __user *to, const void *from, unsigned long n)
+__arch_copy_to_user(void __user *to, const void *from, unsigned long n)
{
#ifndef CONFIG_UACCESS_WITH_MEMCPY
unsigned int __ua_flags;
-
- check_object_size(from, n, true);
__ua_flags = uaccess_save_and_enable();
n = arm_copy_to_user(to, from, n);
uaccess_restore(__ua_flags);
return n;
#else
- check_object_size(from, n, true);
return arm_copy_to_user(to, from, n);
#endif
}
@@ -526,25 +522,49 @@ __clear_user(void __user *addr, unsigned long n)
}
#else
-#define __copy_from_user(to, from, n) (memcpy(to, (void __force *)from, n), 0)
-#define __copy_to_user(to, from, n) (memcpy((void __force *)to, from, n), 0)
+#define __arch_copy_from_user(to, from, n) \
+ (memcpy(to, (void __force *)from, n), 0)
+#define __arch_copy_to_user(to, from, n) \
+ (memcpy((void __force *)to, from, n), 0)
#define __clear_user(addr, n) (memset((void __force *)addr, 0, n), 0)
#endif
-static inline unsigned long __must_check copy_from_user(void *to, const void __user *from, 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_from_user(void *to, const void __user *from, unsigned long n)
{
unsigned long res = n;
+
+ check_object_size(to, n, false);
+
if (likely(access_ok(VERIFY_READ, from, n)))
- res = __copy_from_user(to, from, n);
+ res = __arch_copy_from_user(to, from, n);
if (unlikely(res))
memset(to + (n - res), 0, res);
return res;
}
-static inline unsigned long __must_check copy_to_user(void __user *to, const void *from, unsigned long 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_to_user(void __user *to, const void *from, unsigned long n)
+{
+ check_object_size(from, n, true);
+
if (access_ok(VERIFY_WRITE, to, n))
- n = __copy_to_user(to, from, n);
+ n = __arch_copy_to_user(to, from, n);
return n;
}
--
2.7.4
--
Kees Cook
Pixel Security
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