Commit 3b82a6ea authored by James Morse's avatar James Morse Committed by Catalin Marinas

Revert "arm64: uaccess: implement unsafe accessors"

This reverts commit a1f33941.

The unsafe accessors allow the PAN enable/disable calls to be made
once for a group of accesses. Adding these means we can now have
sequences that look like this:

| user_access_begin();
| unsafe_put_user(static-value, x, err);
| unsafe_put_user(helper-that-sleeps(), x, err);
| user_access_end();

Calling schedule() without taking an exception doesn't switch the
PSTATE or TTBRs. We can switch out of a uaccess-enabled region, and
run other code with uaccess enabled for a different thread.

We can also switch from uaccess-disabled code back into this region,
meaning the unsafe_put_user()s will fault.

For software-PAN, threads that do this will get stuck as
handle_mm_fault() will determine the page has already been mapped in,
but we fault again as the page tables aren't loaded.

To solve this we need code in __switch_to() that save/restores the
PAN state.
Acked-by: default avatarJulien Thierry <julien.thierry@arm.com>
Acked-by: default avatarMark Rutland <mark.rutland@arm.com>
Signed-off-by: default avatarJames Morse <james.morse@arm.com>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 742fafa5
......@@ -276,9 +276,11 @@ static inline void __user *__uaccess_mask_ptr(const void __user *ptr)
: "+r" (err), "=&r" (x) \
: "r" (addr), "i" (-EFAULT))
#define __get_user_err_unsafe(x, ptr, err) \
#define __get_user_err(x, ptr, err) \
do { \
unsigned long __gu_val; \
__chk_user_ptr(ptr); \
uaccess_enable_not_uao(); \
switch (sizeof(*(ptr))) { \
case 1: \
__get_user_asm("ldrb", "ldtrb", "%w", __gu_val, (ptr), \
......@@ -299,24 +301,17 @@ do { \
default: \
BUILD_BUG(); \
} \
(x) = (__force __typeof__(*(ptr)))__gu_val; \
} while (0)
#define __get_user_err_check(x, ptr, err) \
do { \
__chk_user_ptr(ptr); \
uaccess_enable_not_uao(); \
__get_user_err_unsafe((x), (ptr), (err)); \
uaccess_disable_not_uao(); \
(x) = (__force __typeof__(*(ptr)))__gu_val; \
} while (0)
#define __get_user_err(x, ptr, err, accessor) \
#define __get_user_check(x, ptr, err) \
({ \
__typeof__(*(ptr)) __user *__p = (ptr); \
might_fault(); \
if (access_ok(VERIFY_READ, __p, sizeof(*__p))) { \
__p = uaccess_mask_ptr(__p); \
accessor((x), __p, (err)); \
__get_user_err((x), __p, (err)); \
} else { \
(x) = 0; (err) = -EFAULT; \
} \
......@@ -324,14 +319,14 @@ do { \
#define __get_user_error(x, ptr, err) \
({ \
__get_user_err((x), (ptr), (err), __get_user_err_check); \
__get_user_check((x), (ptr), (err)); \
(void)0; \
})
#define __get_user(x, ptr) \
({ \
int __gu_err = 0; \
__get_user_err((x), (ptr), __gu_err, __get_user_err_check); \
__get_user_check((x), (ptr), __gu_err); \
__gu_err; \
})
......@@ -351,9 +346,11 @@ do { \
: "+r" (err) \
: "r" (x), "r" (addr), "i" (-EFAULT))
#define __put_user_err_unsafe(x, ptr, err) \
#define __put_user_err(x, ptr, err) \
do { \
__typeof__(*(ptr)) __pu_val = (x); \
__chk_user_ptr(ptr); \
uaccess_enable_not_uao(); \
switch (sizeof(*(ptr))) { \
case 1: \
__put_user_asm("strb", "sttrb", "%w", __pu_val, (ptr), \
......@@ -374,24 +371,16 @@ do { \
default: \
BUILD_BUG(); \
} \
} while (0)
#define __put_user_err_check(x, ptr, err) \
do { \
__chk_user_ptr(ptr); \
uaccess_enable_not_uao(); \
__put_user_err_unsafe((x), (ptr), (err)); \
uaccess_disable_not_uao(); \
} while (0)
#define __put_user_err(x, ptr, err, accessor) \
#define __put_user_check(x, ptr, err) \
({ \
__typeof__(*(ptr)) __user *__p = (ptr); \
might_fault(); \
if (access_ok(VERIFY_WRITE, __p, sizeof(*__p))) { \
__p = uaccess_mask_ptr(__p); \
accessor((x), __p, (err)); \
__put_user_err((x), __p, (err)); \
} else { \
(err) = -EFAULT; \
} \
......@@ -399,39 +388,19 @@ do { \
#define __put_user_error(x, ptr, err) \
({ \
__put_user_err((x), (ptr), (err), __put_user_err_check); \
__put_user_check((x), (ptr), (err)); \
(void)0; \
})
#define __put_user(x, ptr) \
({ \
int __pu_err = 0; \
__put_user_err((x), (ptr), __pu_err, __put_user_err_check); \
__put_user_check((x), (ptr), __pu_err); \
__pu_err; \
})
#define put_user __put_user
#define user_access_begin() uaccess_enable_not_uao()
#define user_access_end() uaccess_disable_not_uao()
#define unsafe_get_user(x, ptr, err) \
do { \
int __gu_err = 0; \
__get_user_err((x), (ptr), __gu_err, __get_user_err_unsafe); \
if (__gu_err != 0) \
goto err; \
} while (0)
#define unsafe_put_user(x, ptr, err) \
do { \
int __pu_err = 0; \
__put_user_err((x), (ptr), __pu_err, __put_user_err_unsafe); \
if (__pu_err != 0) \
goto err; \
} while (0)
extern unsigned long __must_check __arch_copy_from_user(void *to, const void __user *from, unsigned long n);
#define raw_copy_from_user(to, from, n) \
({ \
......
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