[PATCH v2][wireless-next/for-next] wifi: mt76: mt7996: Use DECLARE_FLEX_ARRAY() and fix -Warray-bounds warnings

Gustavo A. R. Silva
2023-12-12T17:14:42Z

Transform zero-length arrays `rate`, `adm_stat` and `msdu_cnt` into
proper flexible-array members in anonymous union in `struct
mt7996_mcu_all_sta_info_event` via the DECLARE_FLEX_ARRAY()
helper; and fix multiple -Warray-bounds warnings:

drivers/net/wireless/mediatek/mt76/mt7996/mcu.c:544:61: warning: array subscript <unknown> is outside array bounds of 'struct <anonymous>[0]' [-Warray-bounds=]
drivers/net/wireless/mediatek/mt76/mt7996/mcu.c:551:58: warning: array subscript <unknown> is outside array bounds of 'struct <anonymous>[0]' [-Warray-bounds=]
drivers/net/wireless/mediatek/mt76/mt7996/mcu.c:553:58: warning: array subscript <unknown> is outside array bounds of 'struct <anonymous>[0]' [-Warray-bounds=]
drivers/net/wireless/mediatek/mt76/mt7996/mcu.c:530:61: warning: array subscript <unknown> is outside array bounds of 'struct <anonymous>[0]' [-Warray-bounds=]
drivers/net/wireless/mediatek/mt76/mt7996/mcu.c:538:66: warning: array subscript <unknown> is outside array bounds of 'struct <anonymous>[0]' [-Warray-bounds=]
drivers/net/wireless/mediatek/mt76/mt7996/mcu.c:540:66: warning: array subscript <unknown> is outside array bounds of 'struct <anonymous>[0]' [-Warray-bounds=]
drivers/net/wireless/mediatek/mt76/mt7996/mcu.c:520:57: warning: array subscript <unknown> is outside array bounds of 'struct all_sta_trx_rate[0]' [-Warray-bounds=]
drivers/net/wireless/mediatek/mt76/mt7996/mcu.c:526:76: warning: array subscript <unknown> is outside array bounds of 'struct all_sta_trx_rate[0]' [-Warray-bounds=]
drivers/net/wireless/mediatek/mt76/mt7996/mcu.c:526:76: warning: array subscript <unknown> is outside array bounds of 'struct all_sta_trx_rate[0]' [-Warray-bounds=]
drivers/net/wireless/mediatek/mt76/mt7996/mcu.c:526:76: warning: array subscript <unknown> is outside array bounds of 'struct all_sta_trx_rate[0]' [-Warray-bounds=]
drivers/net/wireless/mediatek/mt76/mt7996/mcu.c:526:76: warning: array subscript <unknown> is outside array bounds of 'struct all_sta_trx_rate[0]' [-Warray-bounds=]

This results in no differences in binary output, helps with the ongoing
efforts to globally enable -Warray-bounds.

Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
Changes in v2:
- Add Kees' RB tag.
- Transform zero-length array `rate` into flex-array member.
- Address five more -Warray-bounds warnings introduced by fake
flexible array `rate`

drivers/net/wireless/mediatek/mt76/mt7996/mcu.h | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/net/wireless/mediatek/mt76/mt7996/mcu.h b/drivers/net/wireless/mediatek/mt76/mt7996/mcu.h
index 3e013b20ee5e..36cacc495c75 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7996/mcu.h
+++ b/drivers/net/wireless/mediatek/mt76/mt7996/mcu.h
@@ -206,20 +206,20 @@ struct mt7996_mcu_all_sta_info_event {
u8 rsv3[4];

union {
- struct all_sta_trx_rate rate[0];
- struct {
+ DECLARE_FLEX_ARRAY(struct all_sta_trx_rate, rate);
+ DECLARE_FLEX_ARRAY(struct {
__le16 wlan_idx;
u8 rsv[2];
__le32 tx_bytes[IEEE80211_NUM_ACS];
__le32 rx_bytes[IEEE80211_NUM_ACS];
- } adm_stat[0] __packed;
+ } __packed, adm_stat);

- struct {
+ DECLARE_FLEX_ARRAY(struct {
__le16 wlan_idx;
u8 rsv[2];
__le32 tx_msdu_cnt;
__le32 rx_msdu_cnt;
- } msdu_cnt[0] __packed;
+ } __packed, msdu_cnt);
} __packed;
} __packed;

--
2.34.1