mwifiex: resolve races between async FW init (failure) and device removal

It's possible for the FW init sequence to fail, which will trigger a
device cleanup sequence in mwifiex_fw_dpc(). This sequence can race with
device suspend() or remove() (e.g., reboot or unbind), and can trigger
use-after-free issues. Currently, this driver attempts (poorly) to
synchronize remove() using a semaphore, but it doesn't protect some of
the critical sections properly. Particularly, we grab a pointer to the
adapter struct (card->adapter) without checking if it's being freed or
not. We later do a NULL check on the adapter, but that doesn't work if
the adapter was freed.

Also note that the PCIe interface driver doesn't ever set card->adapter
to NULL, so even if we get the synchronization right, we still might try
to redo the cleanup in ->remove(), even if the FW init failure sequence
already did it.

This patch replaces the static semaphore with a per-device completion
struct, and uses that completion to synchronize the remove() thread with
the mwifiex_fw_dpc(). A future patch will utilize this completion to
synchronize the suspend() thread as well.

Signed-off-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/net/wireless/marvell/mwifiex/pcie.h b/drivers/net/wireless/marvell/mwifiex/pcie.h
index 46f99cae9399..ae3365d1c34e 100644
--- a/drivers/net/wireless/marvell/mwifiex/pcie.h
+++ b/drivers/net/wireless/marvell/mwifiex/pcie.h
@@ -22,6 +22,7 @@
 #ifndef	_MWIFIEX_PCIE_H
 #define	_MWIFIEX_PCIE_H
 
+#include    <linux/completion.h>
 #include    <linux/pci.h>
 #include    <linux/interrupt.h>
 
@@ -345,6 +346,7 @@ struct pcie_service_card {
 	struct pci_dev *dev;
 	struct mwifiex_adapter *adapter;
 	struct mwifiex_pcie_device pcie;
+	struct completion fw_done;
 
 	u8 txbd_flush;
 	u32 txbd_wrptr;