arm64: avoid multiple evaluation of ptr in get_user/put_user()

get_user() is defined as a function macro in arm64, and trace_get_user()
calls it as followed:
     get_user(ch, ptr++);
Since the second parameter occurs twice in the definition, 'ptr++' is
unexpectedly evaluated twice and trace_get_user() will generate a bogus
string from user-provided one. As a result, some ftrace sysfs operations,
like "echo FUNCNAME > set_ftrace_filter," hit this case and eventually fail.
This patch fixes the issue both in get_user() and put_user().

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
[catalin.marinas@arm.com: added __user type annotation and s/optr/__p/]
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

1 files changed, 6 insertions, 4 deletions

diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
index edb3d5c73a32..7ecc2b23882e 100644
--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h
@@ -166,9 +166,10 @@ do {									\
 
 #define get_user(x, ptr)                                                \
 ({                                                                      \
+        __typeof__(*(ptr)) __user *__p = (ptr);                         \
         might_fault();                                                  \
-        access_ok(VERIFY_READ, (ptr), sizeof(*(ptr))) ?                 \
-                __get_user((x), (ptr)) :                                \
+        access_ok(VERIFY_READ, __p, sizeof(*__p)) ?                     \
+                __get_user((x), __p) :                                  \
                 ((x) = 0, -EFAULT);                                     \
 })
 
@@ -227,9 +228,10 @@ do {									\
 
 #define put_user(x, ptr)                                                \
 ({                                                                      \
+        __typeof__(*(ptr)) __user *__p = (ptr);                         \
         might_fault();                                                  \
-        access_ok(VERIFY_WRITE, (ptr), sizeof(*(ptr))) ?                \
-                __put_user((x), (ptr)) :                                \
+        access_ok(VERIFY_WRITE, __p, sizeof(*__p)) ?                    \
+                __put_user((x), __p) :                                  \
                 -EFAULT;                                                \
 })