4.18-stable review patch. If anyone has any objections, please let me know.
------------------
From: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
[ Upstream commit f7a6947cd49b7ff4e03f1b4f7e7b223003d752ca ]
Currently if you build a 32-bit powerpc kernel and use get_user() to
load a u64 value it will fail to build with eg:
kernel/rseq.o: In function `rseq_get_rseq_cs':
kernel/rseq.c:123: undefined reference to `__get_user_bad'
This is hitting the check in __get_user_size() that makes sure the
size we're copying doesn't exceed the size of the destination:
#define __get_user_size(x, ptr, size, retval)
do {
retval = 0;
__chk_user_ptr(ptr);
if (size > sizeof(x))
(x) = __get_user_bad();
Which doesn't immediately make sense because the size of the
destination is u64, but it's not really, because __get_user_check()
etc. internally create an unsigned long and copy into that:
#define __get_user_check(x, ptr, size)
({
long __gu_err = -EFAULT;
unsigned long __gu_val = 0;
The problem being that on 32-bit unsigned long is not big enough to
hold a u64. We can fix this with a trick from hpa in the x86 code, we
statically check the type of x and set the type of __gu_val to either
unsigned long or unsigned long long.
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/powerpc/include/asm/uaccess.h | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)
--- a/arch/powerpc/include/asm/uaccess.h
+++ b/arch/powerpc/include/asm/uaccess.h
@@ -250,10 +250,17 @@ do { \
} \
} while (0)
+/*
+ * This is a type: either unsigned long, if the argument fits into
+ * that type, or otherwise unsigned long long.
+ */
+#define __long_type(x) \
+ __typeof__(__builtin_choose_expr(sizeof(x) > sizeof(0UL), 0ULL, 0UL))
+
#define __get_user_nocheck(x, ptr, size) \
({ \
long __gu_err; \
- unsigned long __gu_val; \
+ __long_type(*(ptr)) __gu_val; \
const __typeof__(*(ptr)) __user *__gu_addr = (ptr); \
__chk_user_ptr(ptr); \
if (!is_kernel_addr((unsigned long)__gu_addr)) \
@@ -267,7 +274,7 @@ do { \
#define __get_user_check(x, ptr, size) \
({ \
long __gu_err = -EFAULT; \
- unsigned long __gu_val = 0; \
+ __long_type(*(ptr)) __gu_val = 0; \
const __typeof__(*(ptr)) __user *__gu_addr = (ptr); \
might_fault(); \
if (access_ok(VERIFY_READ, __gu_addr, (size))) { \
@@ -281,7 +288,7 @@ do { \
#define __get_user_nosleep(x, ptr, size) \
({ \
long __gu_err; \
- unsigned long __gu_val; \
+ __long_type(*(ptr)) __gu_val; \
const __typeof__(*(ptr)) __user *__gu_addr = (ptr); \
__chk_user_ptr(ptr); \
barrier_nospec(); \
