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

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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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71
arch/arm/include/asm/uaccess.h
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@@ -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);