[PATCH][next] wifi: cfg80211: Use __counted_by() in struct wmi_start_scan_cmd and avoid -Wfamnae warning

Gustavo A. R. Silva
2024-03-27T18:50:55Z

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/cfg80211.c:896:43: 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>
---
drivers/net/wireless/ath/wil6210/cfg80211.c | 22 ++++++++++-----------
drivers/net/wireless/ath/wil6210/wmi.h | 2 +-
2 files changed, 11 insertions(+), 13 deletions(-)

diff --git a/drivers/net/wireless/ath/wil6210/cfg80211.c b/drivers/net/wireless/ath/wil6210/cfg80211.c
index dbe4b3478f03..836b49954171 100644
--- a/drivers/net/wireless/ath/wil6210/cfg80211.c
+++ b/drivers/net/wireless/ath/wil6210/cfg80211.c
@@ -892,10 +892,8 @@ static int wil_cfg80211_scan(struct wiphy *wiphy,
struct wil6210_priv *wil = wiphy_to_wil(wiphy);
struct wireless_dev *wdev = request->wdev;
struct wil6210_vif *vif = wdev_to_vif(wil, wdev);
- struct {
- struct wmi_start_scan_cmd cmd;
- u16 chnl[4];
- } __packed cmd;
+ DEFINE_FLEX(struct wmi_start_scan_cmd, cmd,
+ channel_list, num_channels, 4);
uint i, n;
int rc;

@@ -977,9 +975,9 @@ static int wil_cfg80211_scan(struct wiphy *wiphy,
vif->scan_request = request;
mod_timer(&vif->scan_timer, jiffies + WIL6210_SCAN_TO);

- memset(&cmd, 0, sizeof(cmd));
- cmd.cmd.scan_type = WMI_ACTIVE_SCAN;
- cmd.cmd.num_channels = 0;
+ memset(cmd, 0, sizeof(*cmd));
+ cmd->scan_type = WMI_ACTIVE_SCAN;
+ cmd->num_channels = 0;
n = min(request->n_channels, 4U);
for (i = 0; i < n; i++) {
int ch = request->channels[i]->hw_value;
@@ -991,7 +989,8 @@ static int wil_cfg80211_scan(struct wiphy *wiphy,
continue;
}
/* 0-based channel indexes */
- cmd.cmd.channel_list[cmd.cmd.num_channels++].channel = ch - 1;
+ cmd->num_channels++;
+ cmd->channel_list[cmd->num_channels - 1].channel = ch - 1;
wil_dbg_misc(wil, "Scan for ch %d : %d MHz\n", ch,
request->channels[i]->center_freq);
}
@@ -1007,16 +1006,15 @@ static int wil_cfg80211_scan(struct wiphy *wiphy,
if (rc)
goto out_restore;

- if (wil->discovery_mode && cmd.cmd.scan_type == WMI_ACTIVE_SCAN) {
- cmd.cmd.discovery_mode = 1;
+ if (wil->discovery_mode && cmd->scan_type == WMI_ACTIVE_SCAN) {
+ cmd->discovery_mode = 1;
wil_dbg_misc(wil, "active scan with discovery_mode=1\n");
}

if (vif->mid == 0)
wil->radio_wdev = wdev;
rc = wmi_send(wil, WMI_START_SCAN_CMDID, vif->mid,
- &cmd, sizeof(cmd.cmd) +
- cmd.cmd.num_channels * sizeof(cmd.cmd.channel_list[0]));
+ cmd, struct_size(cmd, channel_list, cmd->num_channels));

out_restore:
if (rc) {
diff --git a/drivers/net/wireless/ath/wil6210/wmi.h b/drivers/net/wireless/ath/wil6210/wmi.h
index 71bf2ae27a98..b47606d9068c 100644
--- a/drivers/net/wireless/ath/wil6210/wmi.h
+++ b/drivers/net/wireless/ath/wil6210/wmi.h
@@ -474,7 +474,7 @@ struct wmi_start_scan_cmd {
struct {
u8 channel;
u8 reserved;
- } channel_list[];
+ } channel_list[] __counted_by(num_channels);
} __packed;

#define WMI_MAX_PNO_SSID_NUM (16)
--
2.34.1