[PATCH] [next] HID: hyperv: Replace one-element array with flexible-array member

From: Paulo Miguel Almeida
Date: Mon Oct 17 2022 - 03:51:39 EST


One-element arrays are deprecated, and we are replacing them with
flexible array members instead. So, replace one-element array with
flexible-array member in structs synthhid_msg, synthhid_input_report,
pipe_prt_msg and refactor the rest of the code accordingly.

This helps with the ongoing efforts to tighten the FORTIFY_SOURCE
routines on memcpy() and help us make progress towards globally
enabling -fstrict-flex-arrays=3 [1].

Link: https://github.com/KSPP/linux/issues/79
Link: https://github.com/KSPP/linux/issues/210
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101836 [1]

Signed-off-by: Paulo Miguel Almeida <paulo.miguel.almeida.rodenas@xxxxxxxxx>
---
drivers/hid/hid-hyperv.c | 17 +++++++----------
1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/drivers/hid/hid-hyperv.c b/drivers/hid/hid-hyperv.c
index e0bc73124196..208cf8d981a5 100644
--- a/drivers/hid/hid-hyperv.c
+++ b/drivers/hid/hid-hyperv.c
@@ -61,7 +61,7 @@ struct synthhid_msg_hdr {

struct synthhid_msg {
struct synthhid_msg_hdr header;
- char data[1]; /* Enclosed message */
+ char data[]; /* Enclosed message */
};

union synthhid_version {
@@ -99,7 +99,7 @@ struct synthhid_device_info_ack {

struct synthhid_input_report {
struct synthhid_msg_hdr header;
- char buffer[1];
+ char buffer[];
};

#pragma pack(pop)
@@ -118,7 +118,7 @@ enum pipe_prot_msg_type {
struct pipe_prt_msg {
enum pipe_prot_msg_type type;
u32 size;
- char data[1];
+ char data[];
};

struct mousevsc_prt_msg {
@@ -232,7 +232,7 @@ static void mousevsc_on_receive_device_info(struct mousevsc_dev *input_device,

ret = vmbus_sendpacket(input_device->device->channel,
&ack,
- sizeof(struct pipe_prt_msg) - sizeof(unsigned char) +
+ sizeof(struct pipe_prt_msg) +
sizeof(struct synthhid_device_info_ack),
(unsigned long)&ack,
VM_PKT_DATA_INBAND,
@@ -271,16 +271,14 @@ static void mousevsc_on_receive(struct hv_device *device,
* malicious/buggy hypervisor/host, add a check here to
* ensure we don't corrupt memory.
*/
- if ((pipe_msg->size + sizeof(struct pipe_prt_msg)
- - sizeof(unsigned char))
+ if (struct_size(pipe_msg, data, pipe_msg->size)
> sizeof(struct mousevsc_prt_msg)) {
WARN_ON(1);
break;
}

memcpy(&input_dev->protocol_resp, pipe_msg,
- pipe_msg->size + sizeof(struct pipe_prt_msg) -
- sizeof(unsigned char));
+ struct_size(pipe_msg, data, pipe_msg->size));
complete(&input_dev->wait_event);
break;

@@ -359,8 +357,7 @@ static int mousevsc_connect_to_vsp(struct hv_device *device)
request->request.version_requested.version = SYNTHHID_INPUT_VERSION;

ret = vmbus_sendpacket(device->channel, request,
- sizeof(struct pipe_prt_msg) -
- sizeof(unsigned char) +
+ sizeof(struct pipe_prt_msg) +
sizeof(struct synthhid_protocol_request),
(unsigned long)request,
VM_PKT_DATA_INBAND,
--
2.37.3