[PATCH] wifi: mt76: mt7915: fix use-after-free bugs in mt7915_mac_dump_work()

[Duoming Zhou]

When the mt7915 pci chip is detaching, the mt7915_crash_data is
released in mt7915_coredump_unregister(). However, the work item
dump_work may still be running or pending, leading to UAF bugs
when the already freed crash_data is dereferenced again in
mt7915_mac_dump_work().

The race condition can occur as follows:

CPU 0 (removal path)               | CPU 1 (workqueue)
mt7915_pci_remove()                | mt7915_sys_recovery_set()
 mt7915_unregister_device()        |  mt7915_reset()
  mt7915_coredump_unregister()     |   queue_work()
   vfree(dev->coredump.crash_data) | mt7915_mac_dump_work()
                                   |  crash_data-> // UAF

Fix this by ensuring dump_work is properly canceled before
the crash_data is deallocated. Add cancel_work_sync() in
mt7915_unregister_device() to synchronize with any pending
or executing dump work.

Fixes: 4dbcb9125cc3 ("wifi: mt76: mt7915: enable coredump support")
Signed-off-by: Duoming Zhou <duoming at zju.edu.cn>
---
 drivers/net/wireless/mediatek/mt76/mt7915/init.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/net/wireless/mediatek/mt76/mt7915/init.c b/drivers/net/wireless/mediatek/mt76/mt7915/init.c
index 22443cbc74a..250c2d2479b 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7915/init.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7915/init.c
@@ -1294,6 +1294,7 @@ int mt7915_register_device(struct mt7915_dev *dev)
 
 void mt7915_unregister_device(struct mt7915_dev *dev)
 {
+	cancel_work_sync(&dev->dump_work);
 	mt7915_unregister_ext_phy(dev);
 	mt7915_coredump_unregister(dev);
 	mt7915_unregister_thermal(&dev->phy);
-- 
2.34.1