[PATCH v2][next] wifi: wil6210: wmi: Use __counted_by() in struct wmi_set_link_monitor_cmd and avoid -Wfamnae warning

Gustavo A. R. Silva
2024-03-27T21:43:41Z

Prepare for the coming implementation by GCC and Clang of the
__counted_by attribute. Flexible array members annotated with
__counted_by can have their accesses bounds-checked at run-time
via CONFIG_UBSAN_BOUNDS (for array indexing) and CONFIG_FORTIFY_SOURCE
(for strcpy/memcpy-family functions).

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

So, use the `DEFINE_FLEX()` helper for an on-stack definition 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 warning:
drivers/net/wireless/ath/wil6210/wmi.c:4018:49: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]

Link: https://github.com/KSPP/linux/issues/202
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
Changes in v2:
- Use __struct_size() to get the compile-time size of the flex-struct
instance.

v1:
- Link: https://lore.kernel.org/linux-hardening/ZgRsn72WkHzfCUsa@neat/

drivers/net/wireless/ath/wil6210/wmi.c | 19 +++++++------------
drivers/net/wireless/ath/wil6210/wmi.h | 2 +-
2 files changed, 8 insertions(+), 13 deletions(-)

diff --git a/drivers/net/wireless/ath/wil6210/wmi.c b/drivers/net/wireless/ath/wil6210/wmi.c
index 6fdb77d4c59e..8ff69dc72fb9 100644
--- a/drivers/net/wireless/ath/wil6210/wmi.c
+++ b/drivers/net/wireless/ath/wil6210/wmi.c
@@ -4014,28 +4014,23 @@ int wmi_set_cqm_rssi_config(struct wil6210_priv *wil,
struct net_device *ndev = wil->main_ndev;
struct wil6210_vif *vif = ndev_to_vif(ndev);
int rc;
- struct {
- struct wmi_set_link_monitor_cmd cmd;
- s8 rssi_thold;
- } __packed cmd = {
- .cmd = {
- .rssi_hyst = rssi_hyst,
- .rssi_thresholds_list_size = 1,
- },
- .rssi_thold = rssi_thold,
- };
struct {
struct wmi_cmd_hdr hdr;
struct wmi_set_link_monitor_event evt;
} __packed reply = {
.evt = {.status = WMI_FW_STATUS_FAILURE},
};
+ DEFINE_FLEX(struct wmi_set_link_monitor_cmd, cmd,
+ rssi_thresholds_list, rssi_thresholds_list_size, 1);
+
+ cmd->rssi_hyst = rssi_hyst;
+ cmd->rssi_thresholds_list[0] = rssi_thold;

if (rssi_thold > S8_MAX || rssi_thold < S8_MIN || rssi_hyst > U8_MAX)
return -EINVAL;

- rc = wmi_call(wil, WMI_SET_LINK_MONITOR_CMDID, vif->mid, &cmd,
- sizeof(cmd), WMI_SET_LINK_MONITOR_EVENTID,
+ rc = wmi_call(wil, WMI_SET_LINK_MONITOR_CMDID, vif->mid, cmd,
+ __struct_size(cmd), WMI_SET_LINK_MONITOR_EVENTID,
&reply, sizeof(reply), WIL_WMI_CALL_GENERAL_TO_MS);
if (rc) {
wil_err(wil, "WMI_SET_LINK_MONITOR_CMDID failed, rc %d\n", rc);
diff --git a/drivers/net/wireless/ath/wil6210/wmi.h b/drivers/net/wireless/ath/wil6210/wmi.h
index b47606d9068c..38f64524019e 100644
--- a/drivers/net/wireless/ath/wil6210/wmi.h
+++ b/drivers/net/wireless/ath/wil6210/wmi.h
@@ -3320,7 +3320,7 @@ struct wmi_set_link_monitor_cmd {
u8 rssi_hyst;
u8 reserved[12];
u8 rssi_thresholds_list_size;
- s8 rssi_thresholds_list[];
+ s8 rssi_thresholds_list[] __counted_by(rssi_thresholds_list_size);
} __packed;

/* wmi_link_monitor_event_type */
--
2.34.1