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

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Message-Id: <20210709131641.269666523@linuxfoundation.org>
Date:   Fri,  9 Jul 2021 15:18:53 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Sean Young <sean@...s.org>,
        Stefani Seibold <stefani@...bold.net>,
        Mauro Carvalho Chehab <mchehab@...pensource.com>,
        Matthew Weber <matthew.weber@...lins.com>
Subject: [PATCH 4.14 22/25] kfifo: DECLARE_KIFO_PTR(fifo, u64) does not work on arm 32 bit

From: Sean Young <sean@...s.org>

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@...s.org>
Acked-by: Stefani Seibold <stefani@...bold.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@...pensource.com>
Signed-off-by: Matthew Weber <matthew.weber@...lins.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 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