[PATCH] iwlwifi: iwl-dbg: Use del_timer_sync() before freeing

[Guenter Roeck]

In Chrome OS, a large number of crashes is observed due to corrupted timer
lists. Steven Rostedt pointed out that this usually happens when a timer
is freed while still active, and that the problem is often triggered
by code calling del_timer() instead of del_timer_sync() just before
freeing.

Steven also identified the iwlwifi driver as one of the possible culprits
since it does exactly that.

Reported-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Johannes Berg <johannes.berg@xxxxxxxxx>
Cc: Gregory Greenman <gregory.greenman@xxxxxxxxx>
Fixes: 60e8abd9d3e91 ("iwlwifi: dbg_ini: add periodic trigger new API support")
Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
---
v1 (from RFC):
    Removed Shahar S Matityahu from Cc: and added Gregory Greenman.
    No functional change.

I thought about the need to add a mutex to protect the timer list, but
I convinced myself that it is not necessary because the code adding
the timer list and the code removing it should never be never executed
in parallel.

 drivers/net/wireless/intel/iwlwifi/iwl-dbg-tlv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/wireless/intel/iwlwifi/iwl-dbg-tlv.c b/drivers/net/wireless/intel/iwlwifi/iwl-dbg-tlv.c
index 866a33f49915..3237d4b528b5 100644
--- a/drivers/net/wireless/intel/iwlwifi/iwl-dbg-tlv.c
+++ b/drivers/net/wireless/intel/iwlwifi/iwl-dbg-tlv.c
@@ -371,7 +371,7 @@ void iwl_dbg_tlv_del_timers(struct iwl_trans *trans)
 	struct iwl_dbg_tlv_timer_node *node, *tmp;
 
 	list_for_each_entry_safe(node, tmp, timer_list, list) {
-		del_timer(&node->timer);
+		del_timer_sync(&node->timer);
 		list_del(&node->list);
 		kfree(node);
 	}
-- 
2.35.1