[PATCH v2][next] w1: Avoid -Wflex-array-member-not-at-end warnings

Gustavo A. R. Silva
2025-04-07T19:36:29Z

-Wflex-array-member-not-at-end was introduced in GCC-14, and we are
getting ready to enable it, globally.

Use the `DEFINE_RAW_FLEX()` helper for on-stack definitions of
a flexible structure where the size of the flexible-array member
is known at compile-time, and refactor the rest of the code,
accordingly.

So, with these changes, fix the following warnings:

drivers/w1/w1_netlink.c:198:31: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
drivers/w1/w1_netlink.c:219:31: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
Changes in v2:
- Fix memcpy() instance - use new pointer `pkg_msg`, instead of `packet`. (Kees)

v1:
- Link: https://lore.kernel.org/linux-hardening/Z-WD2NP_1A0ratnI@kspp/

drivers/w1/w1_netlink.c | 42 ++++++++++++++++++++---------------------
1 file changed, 20 insertions(+), 22 deletions(-)

diff --git a/drivers/w1/w1_netlink.c b/drivers/w1/w1_netlink.c
index 691978cddab7..724a008cf342 100644
--- a/drivers/w1/w1_netlink.c
+++ b/drivers/w1/w1_netlink.c
@@ -194,16 +194,16 @@ static void w1_netlink_queue_status(struct w1_cb_block *block,
static void w1_netlink_send_error(struct cn_msg *cn, struct w1_netlink_msg *msg,
int portid, int error)
{
- struct {
- struct cn_msg cn;
- struct w1_netlink_msg msg;
- } packet;
- memcpy(&packet.cn, cn, sizeof(packet.cn));
- memcpy(&packet.msg, msg, sizeof(packet.msg));
- packet.cn.len = sizeof(packet.msg);
- packet.msg.len = 0;
- packet.msg.status = (u8)-error;
- cn_netlink_send(&packet.cn, portid, 0, GFP_KERNEL);
+ DEFINE_RAW_FLEX(struct cn_msg, packet, data,
+ sizeof(struct w1_netlink_msg));
+ struct w1_netlink_msg *pkt_msg = (struct w1_netlink_msg *)packet->data;
+
+ memcpy(packet, cn, sizeof(*packet));
+ memcpy(pkt_msg, msg, sizeof(*pkt_msg));
+ packet->len = sizeof(*pkt_msg);
+ pkt_msg->len = 0;
+ pkt_msg->status = (u8)-error;
+ cn_netlink_send(packet, portid, 0, GFP_KERNEL);
}

/**
@@ -215,22 +215,20 @@ static void w1_netlink_send_error(struct cn_msg *cn, struct w1_netlink_msg *msg,
*/
void w1_netlink_send(struct w1_master *dev, struct w1_netlink_msg *msg)
{
- struct {
- struct cn_msg cn;
- struct w1_netlink_msg msg;
- } packet;
- memset(&packet, 0, sizeof(packet));
+ DEFINE_RAW_FLEX(struct cn_msg, packet, data,
+ sizeof(struct w1_netlink_msg));
+ struct w1_netlink_msg *pkg_msg = (struct w1_netlink_msg *)packet->data;

- packet.cn.id.idx = CN_W1_IDX;
- packet.cn.id.val = CN_W1_VAL;
+ packet->id.idx = CN_W1_IDX;
+ packet->id.val = CN_W1_VAL;

- packet.cn.seq = dev->seq++;
- packet.cn.len = sizeof(*msg);
+ packet->seq = dev->seq++;
+ packet->len = sizeof(*msg);

- memcpy(&packet.msg, msg, sizeof(*msg));
- packet.msg.len = 0;
+ memcpy(pkg_msg, msg, sizeof(*msg));
+ pkg_msg->len = 0;

- cn_netlink_send(&packet.cn, 0, 0, GFP_KERNEL);
+ cn_netlink_send(packet, 0, 0, GFP_KERNEL);
}

static void w1_send_slave(struct w1_master *dev, u64 rn)
--
2.43.0