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Date: Mon, 21 Oct 2013 09:44:37 +0100
From: "Jan Beulich" <JBeulich@...e.com>
To: <mingo@...e.hu>, <tglx@...utronix.de>, <hpa@...or.com>
Cc: <arjan@...ux.intel.com>, <linux-kernel@...r.kernel.org>
Subject: [PATCH 2/2] x86: unify copy_to_user() and add size checking to
it
Similarly to copy_from_user(), where the range check is to protect
against kernel memory corruption, copy_to_user() can benefit from such
checking too: Here it protects against kernel information leaks.
Signed-off-by: Jan Beulich <jbeulich@...e.com>
Cc: Arjan van de Ven <arjan@...ux.intel.com>
---
arch/x86/include/asm/uaccess.h | 30 ++++++++++++++++++++++++++++++
arch/x86/include/asm/uaccess_32.h | 3 ---
arch/x86/include/asm/uaccess_64.h | 10 ----------
arch/x86/lib/usercopy_32.c | 5 ++---
4 files changed, 32 insertions(+), 16 deletions(-)
--- 3.12-rc6-x86.orig/arch/x86/include/asm/uaccess.h
+++ 3.12-rc6-x86/arch/x86/include/asm/uaccess.h
@@ -544,6 +544,8 @@ extern struct movsl_mask {
unsigned long __must_check _copy_from_user(void *to, const void __user *from,
unsigned n);
+unsigned long __must_check _copy_to_user(void __user *to, const void *from,
+ unsigned n);
#ifdef CONFIG_DEBUG_STRICT_USER_COPY_CHECKS
# define copy_user_diag __compiletime_error
@@ -553,6 +555,8 @@ unsigned long __must_check _copy_from_us
extern void copy_user_diag("copy_from_user() buffer size is too small")
copy_from_user_overflow(void);
+extern void copy_user_diag("copy_to_user() buffer size is too small")
+copy_to_user_overflow(void) __asm__("copy_from_user_overflow");
#undef copy_user_diag
@@ -563,6 +567,11 @@ __compiletime_warning("copy_from_user()
__copy_from_user_overflow(void) __asm__("copy_from_user_overflow");
#define __copy_from_user_overflow(size, count) __copy_from_user_overflow()
+extern void
+__compiletime_warning("copy_to_user() buffer size is not provably correct")
+__copy_to_user_overflow(void) __asm__("copy_from_user_overflow");
+#define __copy_to_user_overflow(size, count) __copy_to_user_overflow()
+
#else
static inline void
@@ -571,6 +580,8 @@ __copy_from_user_overflow(int size, unsi
WARN(1, "Buffer overflow detected (%d < %lu)!\n", size, count);
}
+#define __copy_to_user_overflow __copy_from_user_overflow
+
#endif
static inline unsigned long __must_check
@@ -608,7 +619,26 @@ copy_from_user(void *to, const void __us
return n;
}
+static inline unsigned long __must_check
+copy_to_user(void __user *to, const void *from, unsigned long n)
+{
+ int sz = __compiletime_object_size(from);
+
+ might_fault();
+
+ /* See the comment in copy_from_user() above. */
+ if (likely(sz < 0 || sz >= n))
+ n = _copy_to_user(to, from, n);
+ else if(__builtin_constant_p(n))
+ copy_to_user_overflow();
+ else
+ __copy_to_user_overflow(sz, n);
+
+ return n;
+}
+
#undef __copy_from_user_overflow
+#undef __copy_to_user_overflow
#endif /* _ASM_X86_UACCESS_H */
--- 3.12-rc6-x86.orig/arch/x86/include/asm/uaccess_32.h
+++ 3.12-rc6-x86/arch/x86/include/asm/uaccess_32.h
@@ -184,7 +184,4 @@ __copy_from_user_inatomic_nocache(void *
return __copy_from_user_ll_nocache_nozero(to, from, n);
}
-unsigned long __must_check copy_to_user(void __user *to,
- const void *from, unsigned long n);
-
#endif /* _ASM_X86_UACCESS_32_H */
--- 3.12-rc6-x86.orig/arch/x86/include/asm/uaccess_64.h
+++ 3.12-rc6-x86/arch/x86/include/asm/uaccess_64.h
@@ -46,19 +46,9 @@ copy_user_generic(void *to, const void *
}
__must_check unsigned long
-_copy_to_user(void __user *to, const void *from, unsigned len);
-__must_check unsigned long
copy_in_user(void __user *to, const void __user *from, unsigned len);
static __always_inline __must_check
-int copy_to_user(void __user *dst, const void *src, unsigned size)
-{
- might_fault();
-
- return _copy_to_user(dst, src, size);
-}
-
-static __always_inline __must_check
int __copy_from_user(void *dst, const void __user *src, unsigned size)
{
int ret = 0;
--- 3.12-rc6-x86.orig/arch/x86/lib/usercopy_32.c
+++ 3.12-rc6-x86/arch/x86/lib/usercopy_32.c
@@ -654,14 +654,13 @@ EXPORT_SYMBOL(__copy_from_user_ll_nocach
* Returns number of bytes that could not be copied.
* On success, this will be zero.
*/
-unsigned long
-copy_to_user(void __user *to, const void *from, unsigned long n)
+unsigned long _copy_to_user(void __user *to, const void *from, unsigned n)
{
if (access_ok(VERIFY_WRITE, to, n))
n = __copy_to_user(to, from, n);
return n;
}
-EXPORT_SYMBOL(copy_to_user);
+EXPORT_SYMBOL(_copy_to_user);
/**
* copy_from_user: - Copy a block of data from user space.
--
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