[PATCH 4.14 22/25] kfifo: DECLARE_KIFO_PTR(fifo, u64) does not work on arm 32 bit

From: Greg Kroah-Hartman
Date: Fri Jul 09 2021 - 09:20:04 EST

From: Sean Young <sean@xxxxxxxx>

commit 8a866fee3909c49738e1c4429a8d2b9bf27e015d upstream.

If you try to store u64 in a kfifo (or a struct with u64 members),
then the buf member of __STRUCT_KFIFO_PTR will cause 4 bytes
padding due to alignment (note that struct __kfifo is 20 bytes
on 32 bit).

That in turn causes the __is_kfifo_ptr() to fail, which is caught
by kfifo_alloc(), which now returns EINVAL.

So, ensure that __is_kfifo_ptr() compares to the right structure.

Signed-off-by: Sean Young <sean@xxxxxxxx>
Acked-by: Stefani Seibold <stefani@xxxxxxxxxxx>
Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxxx>
Signed-off-by: Matthew Weber <matthew.weber@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

include/linux/kfifo.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/include/linux/kfifo.h
+++ b/include/linux/kfifo.h
@@ -113,7 +113,8 @@ struct kfifo_rec_ptr_2 __STRUCT_KFIFO_PT
* array is a part of the structure and the fifo type where the array is
* outside of the fifo structure.
-#define __is_kfifo_ptr(fifo) (sizeof(*fifo) == sizeof(struct __kfifo))
+#define __is_kfifo_ptr(fifo) \
+ (sizeof(*fifo) == sizeof(STRUCT_KFIFO_PTR(typeof(*(fifo)->type))))

* DECLARE_KFIFO_PTR - macro to declare a fifo pointer object