2022-06-01 20:21:43

by Felix Fietkau

[permalink] [raw]
Subject: [PATCH] mac80211: do not wake queues on a vif that is being stopped

When a vif is being removed and sdata->bss is cleared, __ieee80211_wake_txqs
can still be called on it, which crashes as soon as sdata->bss is being
dereferenced.
To fix this properly, check for SDATA_STATE_RUNNING before waking queues,
and take the fq lock when setting it (to ensure that __ieee80211_wake_txqs
observes the change when running on a different CPU

Signed-off-by: Felix Fietkau <[email protected]>
---
net/mac80211/iface.c | 2 ++
net/mac80211/util.c | 3 +++
2 files changed, 5 insertions(+)

diff --git a/net/mac80211/iface.c b/net/mac80211/iface.c
index 41531478437c..15a73b7fdd75 100644
--- a/net/mac80211/iface.c
+++ b/net/mac80211/iface.c
@@ -377,7 +377,9 @@ static void ieee80211_do_stop(struct ieee80211_sub_if_data *sdata, bool going_do
bool cancel_scan;
struct cfg80211_nan_func *func;

+ spin_lock_bh(&local->fq.lock);
clear_bit(SDATA_STATE_RUNNING, &sdata->state);
+ spin_unlock_bh(&local->fq.lock);

cancel_scan = rcu_access_pointer(local->scan_sdata) == sdata;
if (cancel_scan)
diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index 1e26b5235add..dad42d42aa84 100644
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -301,6 +301,9 @@ static void __ieee80211_wake_txqs(struct ieee80211_sub_if_data *sdata, int ac)
local_bh_disable();
spin_lock(&fq->lock);

+ if (!test_bit(SDATA_STATE_RUNNING, &sdata->state))
+ goto out;
+
if (sdata->vif.type == NL80211_IFTYPE_AP)
ps = &sdata->bss->ps;

--
2.36.1



2022-06-06 06:00:37

by Toke Høiland-Jørgensen

[permalink] [raw]
Subject: Re: [PATCH] mac80211: do not wake queues on a vif that is being stopped

Felix Fietkau <[email protected]> writes:

> When a vif is being removed and sdata->bss is cleared, __ieee80211_wake_txqs
> can still be called on it, which crashes as soon as sdata->bss is being
> dereferenced.
> To fix this properly, check for SDATA_STATE_RUNNING before waking queues,
> and take the fq lock when setting it (to ensure that __ieee80211_wake_txqs
> observes the change when running on a different CPU
>
> Signed-off-by: Felix Fietkau <[email protected]>

I think it's a little ugly to expand usage of fq.lock across more and
more places, I don't really have a good alternative, so:

Acked-by: Toke Høiland-Jørgensen <[email protected]>