sparc64: fix misuses of access_process_vm() in genregs32_[sg]et()

We do need access_process_vm() to access the target's reg_window.
However, access to caller's memory (storing the result in
genregs32_get(), fetching the new values in case of genregs32_set())
should be done by normal uaccess primitives.

Fixes: ad4f9576 ([SPARC64]: Fix user accesses in regset code.)
Cc: stable@kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

arch/sparc/kernel/ptrace_64.c

@@ -572,19 +572,13 @@ static int genregs32_get(struct task_struct *target,
 			for (; count > 0 && pos < 32; count--) {
 				if (access_process_vm(target,
 						      (unsigned long)
-						      &reg_window[pos],
+						      &reg_window[pos++],
 						      &reg, sizeof(reg),
 						      FOLL_FORCE)
 				    != sizeof(reg))
 					return -EFAULT;
-				if (access_process_vm(target,
-						      (unsigned long) u,
-						      &reg, sizeof(reg),
-						      FOLL_FORCE | FOLL_WRITE)
-				    != sizeof(reg))
+				if (put_user(reg, u++))
 					return -EFAULT;
-				pos++;
-				u++;
 			}
 		}
 	}
@@ -684,12 +678,7 @@ static int genregs32_set(struct task_struct *target,
 			}
 		} else {
 			for (; count > 0 && pos < 32; count--) {
-				if (access_process_vm(target,
-						      (unsigned long)
-						      u,
-						      &reg, sizeof(reg),
-						      FOLL_FORCE)
-				    != sizeof(reg))
+				if (get_user(reg, u++))
 					return -EFAULT;
 				if (access_process_vm(target,
 						      (unsigned long)