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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: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Russell King 2015-08-19 11:02:28 +01:00
parent 08446b129b
commit 3fba7e23f7
7 changed files with 97 additions and 21 deletions
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19
arch/arm/include/asm/futex.h
View File

@ -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();

71
arch/arm/include/asm/uaccess.h
View File

@ -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);

6
arch/arm/kernel/armksyms.c
View File

@ -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);

6
arch/arm/lib/clear_user.S
View File

@ -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"

6
arch/arm/lib/copy_from_user.S
View File

@ -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

6
arch/arm/lib/copy_to_user.S
View File

@ -17,7 +17,7 @@
/*
* Prototype:
*
* size_t __copy_to_user(void *to, const void *from, size_t n)
* size_t arm_copy_to_user(void *to, const void *from, size_t n)
*
* Purpose:
*
@ -93,11 +93,11 @@
.text
ENTRY(__copy_to_user_std)
WEAK(__copy_to_user)
WEAK(arm_copy_to_user)
#include "copy_template.S"
ENDPROC(__copy_to_user)
ENDPROC(arm_copy_to_user)
ENDPROC(__copy_to_user_std)
.pushsection .text.fixup,"ax"

4
arch/arm/lib/uaccess_with_memcpy.c
View File

@ -136,7 +136,7 @@ out:
}
unsigned long
__copy_to_user(void __user *to, const void *from, unsigned long n)
arm_copy_to_user(void __user *to, const void *from, unsigned long n)
{
/*
* This test is stubbed out of the main function above to keep
@ -190,7 +190,7 @@ out:
return n;
}
unsigned long __clear_user(void __user *addr, unsigned long n)
unsigned long arm_clear_user(void __user *addr, unsigned long n)
{
/* See rational for this in __copy_to_user() above. */
if (n < 64)