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351dd7d2c8
This patch is based on a BUG as reported by Bongani Hlope at
https://lore.kernel.org/all/20260502125824.425d7159@bongani-mini.home.org.za/
When a channel-switch announcement (CSA) beacon is received,
cfg80211 queues a wiphy work item that eventually calls
mt7921_channel_switch_rx_beacon(). If the station disconnects
(or the channel context is otherwise torn down) between the
time the work is queued and the time it runs, the driver's
dev->new_ctx pointer can already have been cleared to NULL.
mt7921_channel_switch_rx_beacon() then dereferences new_ctx
unconditionally, triggering a NULL pointer dereference at
address 0x0:
BUG: kernel NULL pointer dereference, address: 0000000000000000
RIP: 0010:mt7921_channel_switch_rx_beacon+0x1f/0x100 [mt7921_common]
The same missing guard exists in mt7925_channel_switch_rx_beacon(),
which shares the same code pattern introduced by the same commit.
Add an early-return NULL check for dev->new_ctx in both
mt7921_channel_switch_rx_beacon() and
mt7925_channel_switch_rx_beacon(). When new_ctx is NULL there is
no pending channel switch to process, so returning immediately is
the correct and safe action.
Fixes: 8aa2f59260 ("wifi: mt76: mt7921: introduce CSA support")
Reported-by: Bongani Hlope <developer@hlope.org.za>
Oops-Analysis: http://oops.fenrus.org/reports/lkml/20260502125824.425d7159@bongani-mini.home.org.za/report.html
Link: https://lore.kernel.org/all/20260502125824.425d7159@bongani-mini.home.org.za/
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Cc: linux-wireless@vger.kernel.org
Cc: linux-mediatek@lists.infradead.org
Cc: Felix Fietkau <nbd@nbd.name>
Cc: Lorenzo Bianconi <lorenzo@kernel.org>
Cc: Ryder Lee <ryder.lee@mediatek.com>
Link: https://patch.msgid.link/20260504145107.1329197-1-arjan@linux.intel.com
Signed-off-by: Felix Fietkau <nbd@nbd.name>
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