Commit 3fba7e23 authored by Russell King's avatar Russell King
Browse files

ARM: uaccess: provide uaccess_save_and_enable() and uaccess_restore() 



Provide uaccess_save_and_enable() and uaccess_restore() to permit
control of userspace visibility to the kernel, and hook these into
the appropriate places in the kernel where we need to access
userspace.

Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 08446b12

arch/arm/include/asm/futex.h

+17 −2
Original line number Diff line number Diff line
@@ -22,8 +22,11 @@ 
#ifdef CONFIG_SMP



#define __futex_atomic_op(insn, ret, oldval, tmp, uaddr, oparg)	\

({								\

	unsigned int __ua_flags;				\

	smp_mb();						\

	prefetchw(uaddr);					\

	__ua_flags = uaccess_save_and_enable();			\

	__asm__ __volatile__(					\

	"1:	ldrex	%1, [%3]\n"				\

	"	" insn "\n"					\
@@ -34,12 +37,15 @@ 
	__futex_atomic_ex_table("%5")				\

	: "=&r" (ret), "=&r" (oldval), "=&r" (tmp)		\

	: "r" (uaddr), "r" (oparg), "Ir" (-EFAULT)		\

	: "cc", "memory")

	: "cc", "memory");					\

	uaccess_restore(__ua_flags);				\

})



static inline int

futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,

			      u32 oldval, u32 newval)

{

	unsigned int __ua_flags;

	int ret;

	u32 val;
@@ -49,6 +55,7 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, 
	smp_mb();

	/* Prefetching cannot fault */

	prefetchw(uaddr);

	__ua_flags = uaccess_save_and_enable();

	__asm__ __volatile__("@futex_atomic_cmpxchg_inatomic\n"

	"1:	ldrex	%1, [%4]\n"

	"	teq	%1, %2\n"
@@ -61,6 +68,7 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, 
	: "=&r" (ret), "=&r" (val)

	: "r" (oldval), "r" (newval), "r" (uaddr), "Ir" (-EFAULT)

	: "cc", "memory");

	uaccess_restore(__ua_flags);

	smp_mb();



	*uval = val;
@@ -73,6 +81,8 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, 
#include <asm/domain.h>



#define __futex_atomic_op(insn, ret, oldval, tmp, uaddr, oparg)	\

({								\

	unsigned int __ua_flags = uaccess_save_and_enable();	\

	__asm__ __volatile__(					\

	"1:	" TUSER(ldr) "	%1, [%3]\n"			\

	"	" insn "\n"					\
@@ -81,12 +91,15 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, 
	__futex_atomic_ex_table("%5")				\

	: "=&r" (ret), "=&r" (oldval), "=&r" (tmp)		\

	: "r" (uaddr), "r" (oparg), "Ir" (-EFAULT)		\

	: "cc", "memory")

	: "cc", "memory");					\

	uaccess_restore(__ua_flags);				\

})



static inline int

futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,

			      u32 oldval, u32 newval)

{

	unsigned int __ua_flags;

	int ret = 0;

	u32 val;
@@ -94,6 +107,7 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, 
		return -EFAULT;



	preempt_disable();

	__ua_flags = uaccess_save_and_enable();

	__asm__ __volatile__("@futex_atomic_cmpxchg_inatomic\n"

	"1:	" TUSER(ldr) "	%1, [%4]\n"

	"	teq	%1, %2\n"
@@ -103,6 +117,7 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, 
	: "+r" (ret), "=&r" (val)

	: "r" (oldval), "r" (newval), "r" (uaddr), "Ir" (-EFAULT)

	: "cc", "memory");

	uaccess_restore(__ua_flags);



	*uval = val;

	preempt_enable();

arch/arm/include/asm/uaccess.h

+66 −5
Original line number Diff line number Diff line
@@ -49,6 +49,21 @@ struct exception_table_entry 


extern int fixup_exception(struct pt_regs *regs);



/*

 * These two functions allow hooking accesses to userspace to increase

 * system integrity by ensuring that the kernel can not inadvertantly

 * perform such accesses (eg, via list poison values) which could then

 * be exploited for priviledge escalation.

 */

static inline unsigned int uaccess_save_and_enable(void)

{

	return 0;

}



static inline void uaccess_restore(unsigned int flags)

{

}



/*

 * These two are intentionally not defined anywhere - if the kernel

 * code generates any references to them, that's a bug.
@@ -165,6 +180,7 @@ extern int __get_user_64t_4(void *); 
		register typeof(x) __r2 asm("r2");			\

		register unsigned long __l asm("r1") = __limit;		\

		register int __e asm("r0");				\

		unsigned int __ua_flags = uaccess_save_and_enable();	\

		switch (sizeof(*(__p))) {				\

		case 1:							\

			if (sizeof((x)) >= 8)				\
@@ -192,6 +208,7 @@ extern int __get_user_64t_4(void *); 
			break;						\

		default: __e = __get_user_bad(); break;			\

		}							\

		uaccess_restore(__ua_flags);				\

		x = (typeof(*(p))) __r2;				\

		__e;							\

	})
@@ -224,6 +241,7 @@ extern int __put_user_8(void *, unsigned long long); 
		register const typeof(*(p)) __user *__p asm("r0") = __tmp_p; \

		register unsigned long __l asm("r1") = __limit;		\

		register int __e asm("r0");				\

		unsigned int __ua_flags = uaccess_save_and_enable();	\

		switch (sizeof(*(__p))) {				\

		case 1:							\

			__put_user_x(__r2, __p, __e, __l, 1);		\
@@ -239,6 +257,7 @@ extern int __put_user_8(void *, unsigned long long); 
			break;						\

		default: __e = __put_user_bad(); break;			\

		}							\

		uaccess_restore(__ua_flags);				\

		__e;							\

	})
@@ -300,14 +319,17 @@ static inline void set_fs(mm_segment_t fs) 
do {									\

	unsigned long __gu_addr = (unsigned long)(ptr);			\

	unsigned long __gu_val;						\

	unsigned int __ua_flags;					\

	__chk_user_ptr(ptr);						\

	might_fault();							\

	__ua_flags = uaccess_save_and_enable();				\

	switch (sizeof(*(ptr))) {					\

	case 1:	__get_user_asm_byte(__gu_val, __gu_addr, err);	break;	\

	case 2:	__get_user_asm_half(__gu_val, __gu_addr, err);	break;	\

	case 4:	__get_user_asm_word(__gu_val, __gu_addr, err);	break;	\

	default: (__gu_val) = __get_user_bad();				\

	}								\

	uaccess_restore(__ua_flags);					\

	(x) = (__typeof__(*(ptr)))__gu_val;				\

} while (0)
@@ -381,9 +403,11 @@ do { \ 
#define __put_user_err(x, ptr, err)					\

do {									\

	unsigned long __pu_addr = (unsigned long)(ptr);			\

	unsigned int __ua_flags;					\

	__typeof__(*(ptr)) __pu_val = (x);				\

	__chk_user_ptr(ptr);						\

	might_fault();							\

	__ua_flags = uaccess_save_and_enable();				\

	switch (sizeof(*(ptr))) {					\

	case 1: __put_user_asm_byte(__pu_val, __pu_addr, err);	break;	\

	case 2: __put_user_asm_half(__pu_val, __pu_addr, err);	break;	\
@@ -391,6 +415,7 @@ do { \ 
	case 8:	__put_user_asm_dword(__pu_val, __pu_addr, err);	break;	\

	default: __put_user_bad();					\

	}								\

	uaccess_restore(__ua_flags);					\

} while (0)



#define __put_user_asm_byte(x, __pu_addr, err)			\
@@ -474,11 +499,46 @@ do { \ 




#ifdef CONFIG_MMU

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 __copy_to_user_std(void __user *to, const void *from, unsigned long n);

extern unsigned long __must_check __clear_user(void __user *addr, unsigned long n);

extern unsigned long __must_check __clear_user_std(void __user *addr, unsigned long n);

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)

{

	unsigned int __ua_flags = uaccess_save_and_enable();

	n = arm_copy_from_user(to, from, n);

	uaccess_restore(__ua_flags);

	return n;

}



extern unsigned long __must_check

arm_copy_to_user(void __user *to, const void *from, unsigned long n);

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)

{

	unsigned int __ua_flags = uaccess_save_and_enable();

	n = arm_copy_to_user(to, from, n);

	uaccess_restore(__ua_flags);

	return n;

}



extern unsigned long __must_check

arm_clear_user(void __user *addr, unsigned long n);

extern unsigned long __must_check

__clear_user_std(void __user *addr, unsigned long n);



static inline unsigned long __must_check

__clear_user(void __user *addr, unsigned long n)

{

	unsigned int __ua_flags = uaccess_save_and_enable();

	n = arm_clear_user(addr, n);

	uaccess_restore(__ua_flags);

	return 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)
@@ -511,6 +571,7 @@ static inline unsigned long __must_check clear_user(void __user *to, unsigned lo 
	return n;

}



/* These are from lib/ code, and use __get_user() and friends */

extern long strncpy_from_user(char *dest, const char __user *src, long count);



extern __must_check long strlen_user(const char __user *str);

arch/arm/kernel/armksyms.c

+3 −3
Original line number Diff line number Diff line
@@ -91,9 +91,9 @@ EXPORT_SYMBOL(__memzero); 
#ifdef CONFIG_MMU

EXPORT_SYMBOL(copy_page);



EXPORT_SYMBOL(__copy_from_user);

EXPORT_SYMBOL(__copy_to_user);

EXPORT_SYMBOL(__clear_user);

EXPORT_SYMBOL(arm_copy_from_user);

EXPORT_SYMBOL(arm_copy_to_user);

EXPORT_SYMBOL(arm_clear_user);



EXPORT_SYMBOL(__get_user_1);

EXPORT_SYMBOL(__get_user_2);

arch/arm/lib/clear_user.S

+3 −3
Original line number Diff line number Diff line
@@ -12,14 +12,14 @@ 


		.text



/* Prototype: int __clear_user(void *addr, size_t sz)

/* Prototype: unsigned long arm_clear_user(void *addr, size_t sz)

 * Purpose  : clear some user memory

 * Params   : addr - user memory address to clear

 *          : sz   - number of bytes to clear

 * Returns  : number of bytes NOT cleared

 */

ENTRY(__clear_user_std)

WEAK(__clear_user)

WEAK(arm_clear_user)

		stmfd	sp!, {r1, lr}

		mov	r2, #0

		cmp	r1, #4
@@ -44,7 +44,7 @@ WEAK(__clear_user) 
USER(		strnebt	r2, [r0])

		mov	r0, #0

		ldmfd	sp!, {r1, pc}

ENDPROC(__clear_user)

ENDPROC(arm_clear_user)

ENDPROC(__clear_user_std)



		.pushsection .text.fixup,"ax"

arch/arm/lib/copy_from_user.S

+3 −3
Original line number Diff line number Diff line
@@ -17,7 +17,7 @@ 
/*

 * Prototype:

 *

 *	size_t __copy_from_user(void *to, const void *from, size_t n)

 *	size_t arm_copy_from_user(void *to, const void *from, size_t n)

 *

 * Purpose:

 *
@@ -89,11 +89,11 @@ 


	.text



ENTRY(__copy_from_user)

ENTRY(arm_copy_from_user)



#include "copy_template.S"



ENDPROC(__copy_from_user)

ENDPROC(arm_copy_from_user)



	.pushsection .fixup,"ax"

	.align 0

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