linux-kernel - [PATCH][next] SCSI: fusion: mpi_ioc.h: Replace one-element array with flexible-array member

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Date:   Wed, 24 Mar 2021 18:00:36 -0500
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     Sathya Prakash <sathya.prakash@...adcom.com>,
        Sreekanth Reddy <sreekanth.reddy@...adcom.com>,
        Suganath Prabu Subramani 
        <suganath-prabu.subramani@...adcom.com>
Cc:     MPT-FusionLinux.pdl@...adcom.com, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        linux-hardening@...r.kernel.org
Subject: [PATCH][next] SCSI: fusion: mpi_ioc.h: Replace one-element array
 with flexible-array member

There is a regular need in the kernel to provide a way to declare having
a dynamically sized set of trailing elements in a structure. Kernel code
should always use “flexible array members”[1] for these cases. The older
style of one-element or zero-length arrays should no longer be used[2].

Also, this helps with the ongoing efforts to enable -Warray-bounds by
fixing the following warning:

drivers/message/fusion/mptbase.c: In function ‘mptbase_reply’:
drivers/message/fusion/mptbase.c:7747:62: warning: array subscript 1 is above array bounds of ‘U32[1]’ {aka ‘unsigned int[1]’} [-Warray-bounds]
 7747 |     ioc->events[idx].data[ii] = le32_to_cpu(pEventReply->Data[ii]);
./include/uapi/linux/byteorder/little_endian.h:34:51: note: in definition of macro ‘__le32_to_cpu’
   34 | #define __le32_to_cpu(x) ((__force __u32)(__le32)(x))
      |                                                   ^
drivers/message/fusion/mptbase.c:7747:33: note: in expansion of macro ‘le32_to_cpu’
 7747 |     ioc->events[idx].data[ii] = le32_to_cpu(pEventReply->Data[ii]);
      | 

[1] https://en.wikipedia.org/wiki/Flexible_array_member
[2] https://www.kernel.org/doc/html/v5.10/process/deprecated.html#zero-length-and-one-element-arrays

Link: https://github.com/KSPP/linux/issues/79
Link: https://github.com/KSPP/linux/issues/109
Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
---
 drivers/message/fusion/lsi/mpi_ioc.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/message/fusion/lsi/mpi_ioc.h b/drivers/message/fusion/lsi/mpi_ioc.h
index c249f2994fc1..1534460fd5b1 100644
--- a/drivers/message/fusion/lsi/mpi_ioc.h
+++ b/drivers/message/fusion/lsi/mpi_ioc.h
@@ -448,7 +448,7 @@ typedef struct _MSG_EVENT_NOTIFY_REPLY
      U32                    IOCLogInfo;                 /* 10h */
      U32                    Event;                      /* 14h */
      U32                    EventContext;               /* 18h */
-     U32                    Data[1];                    /* 1Ch */
+     U32                    Data[];			/* 1Ch */
 } MSG_EVENT_NOTIFY_REPLY, MPI_POINTER PTR_MSG_EVENT_NOTIFY_REPLY,
   EventNotificationReply_t, MPI_POINTER pEventNotificationReply_t;
 
-- 
2.27.0