linux-kernel - [PATCH][next] media: venus: hfi_msgs.h: Replace one-element arrays with flexible-array members

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Date:   Wed, 10 Feb 2021 18:10:44 -0600
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     Stanimir Varbanov <stanimir.varbanov@...aro.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>
Cc:     linux-media@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        linux-hardening@...r.kernel.org
Subject: [PATCH][next] media: venus: hfi_msgs.h: Replace one-element arrays
 with flexible-array members

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].

Use flexible-array members in struct hfi_msg_sys_property_info_pkt and
hfi_msg_session_property_info_pkt instead of one-element arrays.

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

  CC [M]  drivers/media/platform/qcom/venus/hfi_msgs.o
drivers/media/platform/qcom/venus/hfi_msgs.c: In function ‘hfi_sys_property_info’:
drivers/media/platform/qcom/venus/hfi_msgs.c:246:35: warning: array subscript 1 is above array bounds of ‘u32[1]’ {aka ‘unsigned int[1]’} [-Warray-bounds]
  246 |  if (req_bytes < 128 || !pkt->data[1] || pkt->num_properties > 1)
      |                          ~~~~~~~~~^~~
drivers/media/platform/qcom/venus/hfi_msgs.c: In function ‘hfi_session_prop_info’:
drivers/media/platform/qcom/venus/hfi_msgs.c:342:62: warning: array subscript 1 is above array bounds of ‘u32[1]’ {aka ‘unsigned int[1]’} [-Warray-bounds]
  342 |  if (!req_bytes || req_bytes % sizeof(*buf_req) || !pkt->data[1])
      |                                                     ~~~~~~~~~^~~

[1] https://en.wikipedia.org/wiki/Flexible_array_member
[2] https://www.kernel.org/doc/html/v5.9/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
Build-tested-by: <lkp@...el.com>
Link: https://lore.kernel.org/lkml/6023dd80.MmTeFf8SzwX0iK7%2F%25lkp@intel.com/
Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
---
 drivers/media/platform/qcom/venus/hfi_msgs.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/media/platform/qcom/venus/hfi_msgs.h b/drivers/media/platform/qcom/venus/hfi_msgs.h
index 526d9f5b487b..e2d2ccfbdd24 100644
--- a/drivers/media/platform/qcom/venus/hfi_msgs.h
+++ b/drivers/media/platform/qcom/venus/hfi_msgs.h
@@ -113,7 +113,7 @@ struct hfi_msg_sys_ping_ack_pkt {
 struct hfi_msg_sys_property_info_pkt {
 	struct hfi_pkt_hdr hdr;
 	u32 num_properties;
-	u32 data[1];
+	u32 data[];
 };
 
 struct hfi_msg_session_load_resources_done_pkt {
@@ -233,7 +233,7 @@ struct hfi_msg_session_parse_sequence_header_done_pkt {
 struct hfi_msg_session_property_info_pkt {
 	struct hfi_session_hdr_pkt shdr;
 	u32 num_properties;
-	u32 data[1];
+	u32 data[];
 };
 
 struct hfi_msg_session_release_resources_done_pkt {
-- 
2.27.0