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, 8 insertions, 3 deletions

diff --git a/drivers/net/wireless/marvell/mwifiex/main.h b/drivers/net/wireless/marvell/mwifiex/main.h
index 904a2edefc06..cf4c78080d94 100644
--- a/drivers/net/wireless/marvell/mwifiex/main.h
+++ b/drivers/net/wireless/marvell/mwifiex/main.h
@@ -20,6 +20,7 @@
 #ifndef _MWIFIEX_MAIN_H_
 #define _MWIFIEX_MAIN_H_
 
+#include <linux/completion.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/sched.h>
@@ -985,7 +986,10 @@ struct mwifiex_adapter {
 	u32 usr_dot_11ac_mcs_support;
 
 	atomic_t pending_bridged_pkts;
-	struct semaphore *card_sem;
+
+	/* For synchronizing FW initialization with device lifecycle. */
+	struct completion *fw_done;
+
 	bool ext_scan;
 	u8 fw_api_ver;
 	u8 key_api_major_ver, key_api_minor_ver;
@@ -1438,10 +1442,11 @@ static inline void mwifiex_enable_wake(struct mwifiex_adapter *adapter)
 
 int mwifiex_init_shutdown_fw(struct mwifiex_private *priv,
 			     u32 func_init_shutdown);
-int mwifiex_add_card(void *card, struct semaphore *sem,
+
+int mwifiex_add_card(void *card, struct completion *fw_done,
 		     struct mwifiex_if_ops *if_ops, u8 iface_type,
 		     struct device *dev);
-int mwifiex_remove_card(struct mwifiex_adapter *, struct semaphore *);
+int mwifiex_remove_card(struct mwifiex_adapter *adapter);
 
 void mwifiex_get_version(struct mwifiex_adapter *adapter, char *version,
 			 int maxlen);