Revert "arm64: uaccess: implement unsafe accessors"

This reverts commit a1f33941f7e103bcf471eaf8461b212223c642d6.

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: Julien Thierry <julien.thierry@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

1 files changed, 15 insertions, 46 deletions

diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
index 8ac6e34922e7..07c34087bd5e 100644
--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h
@@ -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)                                 \
 ({                                                                      \