linux-kernel - [PATCH 03/11] mwifiex: Don't release cmd_pending_q

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Date:   Fri, 12 May 2017 09:42:00 -0700
From:   Brian Norris <briannorris@...omium.org>
To:     Ganapathi Bhat <gbhat@...vell.com>,
        Nishant Sarmukadam <nishants@...vell.com>
Cc:     <linux-kernel@...r.kernel.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Amitkumar Karwar <amitkarwar@...il.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        linux-wireless@...r.kernel.org,
        Doug Anderson <dianders@...omium.org>,
        Brian Norris <briannorris@...omium.org>
Subject: [PATCH 03/11] mwifiex: Don't release cmd_pending_q_lock while iterating

From: Douglas Anderson <dianders@...omium.org>

Just like in the previous patch ("mwifiex: Don't release
tx_ba_stream_tbl_lock while iterating"), in
mwifiex_cancel_all_pending_cmd() we were itearting over a list protected
by a spinlock.  Again, it is not safe to release the spinlock while
iterating.  Don't do it.

Luckily in this case there should be no need to release the spinlock.
This is evidenced by:

1. The only function called while the spinlock was released was
   mwifiex_recycle_cmd_node()
2. Aside from atomic functions (which are safe to call), the only
   function called by mwifiex_recycle_cmd_node() was
   mwifiex_insert_cmd_to_free_q().
3. It can be seen in mwifiex_cancel_pending_scan_cmd() that it's OK to
   call mwifiex_insert_cmd_to_free_q() while holding a different
   spinlock (scan_pending_q_lock), so in general holding a spinlock
   should be OK.
4. It doesn't appear that mwifiex_insert_cmd_to_free_q() has any
   interaction with the cmd_pending_q_lock

No known bugs are fixed with this change, but as with other similar
changes this could fix random list corruption.

Signed-off-by: Douglas Anderson <dianders@...omium.org>
Signed-off-by: Brian Norris <briannorris@...omium.org>
---
 drivers/net/wireless/marvell/mwifiex/cmdevt.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/net/wireless/marvell/mwifiex/cmdevt.c b/drivers/net/wireless/marvell/mwifiex/cmdevt.c
index 0c3b217247b1..5fd6c53d7b06 100644
--- a/drivers/net/wireless/marvell/mwifiex/cmdevt.c
+++ b/drivers/net/wireless/marvell/mwifiex/cmdevt.c
@@ -1056,12 +1056,10 @@ mwifiex_cancel_all_pending_cmd(struct mwifiex_adapter *adapter)
 	list_for_each_entry_safe(cmd_node, tmp_node,
 				 &adapter->cmd_pending_q, list) {
 		list_del(&cmd_node->list);
-		spin_unlock_irqrestore(&adapter->cmd_pending_q_lock, flags);

 		if (cmd_node->wait_q_enabled)
 			adapter->cmd_wait_q.status = -1;
 		mwifiex_recycle_cmd_node(adapter, cmd_node);
-		spin_lock_irqsave(&adapter->cmd_pending_q_lock, flags);
 	}
 	spin_unlock_irqrestore(&adapter->cmd_pending_q_lock, flags);
 	spin_unlock_irqrestore(&adapter->mwifiex_cmd_lock, cmd_flags);
-- 
2.13.0.rc2.291.g57267f2277-goog