[PATCH] wifi: mt76: mt7996: fix reading zeroed info->control.flags after mt76_tx_status_skb_add()
lorenzo at kernel.org
lorenzo at kernel.org
Sun May 31 05:02:12 PDT 2026
On May 31, Ryder Lee wrote:
> On Sun, 2026-05-31 at 09:09 +0200, lorenzo at kernel.org wrote:
> > > On Sat, 2026-05-30 at 17:25 +0200, Lorenzo Bianconi wrote:
> > > > mt76_tx_status_skb_add() zeroes the mt76_tx_cb struct stored at
> > > > info->status.status_driver_data via memset(). Since info->control
> > > > and
> > > > info->status are members of the same union in ieee80211_tx_info,
> > > > this overwrites info->control.flags.
> > > > In mt7996_tx_prepare_skb(), mt76_tx_status_skb_add() is called
> > > > before
> > > > mt7996_mac_write_txwi(), which re-reads info->control.flags to
> > > > extract
> > > > IEEE80211_TX_CTRL_MLO_LINK. Because the field has been zeroed,
> > > > the
> > > > link_id always resolves to 0 for frames using global_wcid,
> > > > leading to
> > > > incorrect TXWI configuration.
> > > > Fix this by passing link_id as an explicit parameter to
> > > > mt7996_mac_write_txwi(). In mt7996_tx_prepare_skb(), the link_id
> > > > is
> > > > already extracted from info->control.flags before the destructive
> > > > mt76_tx_status_skb_add() call. For the beacon and inband
> > > > discovery
> > > > callers in mcu.c, use link_conf->link_id directly.
> > > >
> > > > Fixes: f0b0b239b8f36 ("wifi: mt76: mt7996: rework
> > > > mt7996_mac_write_txwi() for MLO support")
> > > > Signed-off-by: Lorenzo Bianconi <lorenzo at kernel.org>
> > > > ---
> > > > drivers/net/wireless/mediatek/mt76/mt7996/mac.c | 9 +++------
> > > > drivers/net/wireless/mediatek/mt76/mt7996/mcu.c | 5 +++--
> > > > drivers/net/wireless/mediatek/mt76/mt7996/mt7996.h | 3 ++-
> > > > 3 files changed, 8 insertions(+), 9 deletions(-)
> > > >
> > > > diff --git a/drivers/net/wireless/mediatek/mt76/mt7996/mac.c
> > > > b/drivers/net/wireless/mediatek/mt76/mt7996/mac.c
> > > > index c98446057282..2d3f80b3e41a 100644
> > > > --- a/drivers/net/wireless/mediatek/mt76/mt7996/mac.c
> > > > +++ b/drivers/net/wireless/mediatek/mt76/mt7996/mac.c
> > > > @@ -856,7 +856,8 @@ mt7996_mac_write_txwi_80211(struct mt7996_dev
> > > > *dev, __le32 *txwi,
> > > > void mt7996_mac_write_txwi(struct mt7996_dev *dev, __le32 *txwi,
> > > > struct sk_buff *skb, struct mt76_wcid
> > > > *wcid,
> > > > struct ieee80211_key_conf *key, int
> > > > pid,
> > > > - enum mt76_txq_id qid, u32 changed)
> > > > + enum mt76_txq_id qid, u32 changed,
> > > > + unsigned int link_id)
> > > > {
> > > > struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb-
> > > > > data;
> > > > struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
> > > > @@ -866,7 +867,6 @@ void mt7996_mac_write_txwi(struct mt7996_dev
> > > > *dev, __le32 *txwi,
> > > > bool is_8023 = info->flags &
> > > > IEEE80211_TX_CTL_HW_80211_ENCAP;
> > > > struct mt76_vif_link *mlink = NULL;
> > > > struct mt7996_vif *mvif;
> > > > - unsigned int link_id;
> > > > u16 tx_count = 15;
> > > > u32 val;
> > > > bool inband_disc = !!(changed &
> > > > (BSS_CHANGED_UNSOL_BCAST_PROBE_RESP |
> > > > @@ -876,9 +876,6 @@ void mt7996_mac_write_txwi(struct mt7996_dev
> > > > *dev, __le32 *txwi,
> > > >
> > > > if (wcid != &dev->mt76.global_wcid)
> > > > link_id = wcid->link_id;
> > > > - else
> > > > - link_id = u32_get_bits(info->control.flags,
> > > > -
> > > > IEEE80211_TX_CTRL_MLO_LINK);
> > > >
> > > > mvif = vif ? (struct mt7996_vif *)vif->drv_priv : NULL;
> > > > if (mvif) {
> > > > @@ -1096,7 +1093,7 @@ int mt7996_tx_prepare_skb(struct mt76_dev
> > > > *mdev, void *txwi_ptr,
> > > > /* Transmit non qos data by 802.11 header and need to
> > > > fill
> > > > txd by host*/
> > > > if (!is_8023 || pid >= MT_PACKET_ID_FIRST)
> > > > mt7996_mac_write_txwi(dev, txwi_ptr, tx_info-
> > > > >skb,
> > > > wcid, key,
> > > > - pid, qid, 0);
> > > > + pid, qid, 0, link_id);
> > > >
> > > > /* MT7996 and MT7992 require driver to provide the MAC
> > > > TXP
> > > > for AddBA
> > > > * req
> > > > diff --git a/drivers/net/wireless/mediatek/mt76/mt7996/mcu.c
> > > > b/drivers/net/wireless/mediatek/mt76/mt7996/mcu.c
> > > > index 8be40d60ad29..a14c63438923 100644
> > > > --- a/drivers/net/wireless/mediatek/mt76/mt7996/mcu.c
> > > > +++ b/drivers/net/wireless/mediatek/mt76/mt7996/mcu.c
> > > > @@ -3103,7 +3103,7 @@ mt7996_mcu_beacon_cont(struct mt7996_dev
> > > > *dev,
> > > >
> > > > buf = (u8 *)bcn + sizeof(*bcn);
> > > > mt7996_mac_write_txwi(dev, (__le32 *)buf, skb, wcid,
> > > > NULL,
> > > > 0, 0,
> > > > - BSS_CHANGED_BEACON);
> > > > + BSS_CHANGED_BEACON, link_conf-
> > > > > link_id);
> > > >
> > > > memcpy(buf + MT_TXD_SIZE, skb->data, skb->len);
> > > > }
> > > > @@ -3249,7 +3249,8 @@ int mt7996_mcu_beacon_inband_discov(struct
> > > > mt7996_dev *dev,
> > > >
> > > > buf = (u8 *)tlv + sizeof(*discov);
> > > >
> > > > - mt7996_mac_write_txwi(dev, (__le32 *)buf, skb, wcid,
> > > > NULL,
> > > > 0, 0, changed);
> > > > + mt7996_mac_write_txwi(dev, (__le32 *)buf, skb, wcid,
> > > > NULL,
> > > > 0, 0,
> > > > + changed, link_conf->link_id);
> > > >
> > > > memcpy(buf + MT_TXD_SIZE, skb->data, skb->len);
> > > >
> > > > diff --git a/drivers/net/wireless/mediatek/mt76/mt7996/mt7996.h
> > > > b/drivers/net/wireless/mediatek/mt76/mt7996/mt7996.h
> > > > index 0dc4198fcf8b..0d6488522ba7 100644
> > > > --- a/drivers/net/wireless/mediatek/mt76/mt7996/mt7996.h
> > > > +++ b/drivers/net/wireless/mediatek/mt76/mt7996/mt7996.h
> > > > @@ -874,7 +874,8 @@ void mt7996_mac_enable_nf(struct mt7996_dev
> > > > *dev,
> > > > u8 band);
> > > > void mt7996_mac_write_txwi(struct mt7996_dev *dev, __le32 *txwi,
> > > > struct sk_buff *skb, struct mt76_wcid
> > > > *wcid,
> > > > struct ieee80211_key_conf *key, int
> > > > pid,
> > > > - enum mt76_txq_id qid, u32 changed);
> > > > + enum mt76_txq_id qid, u32 changed,
> > > > + unsigned int link_id);
> > > > void mt7996_mac_update_beacons(struct mt7996_phy *phy);
> > > > void mt7996_mac_set_coverage_class(struct mt7996_phy *phy);
> > > > void mt7996_mac_work(struct work_struct *work);
> > >
> > > The reason we didn't make the same change is because we use other
> > > control flags (IEEE80211_TX_CTRL*) of info->control.flags not just
> > > MLO
> > > one. So with this change we still need to copy over the other flags
> > > and
> > > pass them in as well.
> >
> > Do you mean you are using info->control.flags in
> > mt7996_mac_write_txwi() in
> > some downstream code? If so, I guess you can use a similar approach
> > and
> > just pass the required field. Copy the full ieee80211_tx_info struct
> > on
> > per-packet basis seems unnecessary.
> >
> > Regards,
> > Lorenzo
> > >
> > >
>
> We will use 3 mac80211_tx_control_flags (i.e.
> IEEE80211_TX_CTRL_RATE_INJECT), so it's better to at least copy info-
> >control.flags directly and pass them in. If you pass each
> individually, the function will end up with 12 parameters, and if more
> flags are needed in the future, you will have to add even more.
But this is necessary for non-upstream code IIUC. Are you going to post it
upstream along with the fix?
I guess it is better to align the link_id used in mt7996_mac_write_txwi()
to the one used in mt7996_mac_write_txwi(). Please take a look to v3.
Regards,
Lorenzo
>
> Ryder
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 228 bytes
Desc: not available
URL: <http://lists.infradead.org/pipermail/linux-arm-kernel/attachments/20260531/309c7d78/attachment.sig>
More information about the linux-arm-kernel
mailing list