Patch "ath9k: hif_usb: fix race condition between usb_get_urb() and usb_kill_anchored_urbs()" has been added to the 5.8-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    ath9k: hif_usb: fix race condition between usb_get_urb() and usb_kill_anchored_urbs()

to the 5.8-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     ath9k-hif_usb-fix-race-condition-between-usb_get_urb.patch
and it can be found in the queue-5.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 5d666a1400db78d496c2f5eb1faf33c8b4f53d63
Author: Brooke Basile <brookebasile@xxxxxxxxx>
Date:   Fri Sep 11 03:14:27 2020 -0400

    ath9k: hif_usb: fix race condition between usb_get_urb() and usb_kill_anchored_urbs()
    
    [ Upstream commit 03fb92a432ea5abe5909bca1455b7e44a9380480 ]
    
    Calls to usb_kill_anchored_urbs() after usb_kill_urb() on multiprocessor
    systems create a race condition in which usb_kill_anchored_urbs() deallocates
    the URB before the completer callback is called in usb_kill_urb(), resulting
    in a use-after-free.
    To fix this, add proper lock protection to usb_kill_urb() calls that can
    possibly run concurrently with usb_kill_anchored_urbs().
    
    Reported-by: syzbot+89bd486af9427a9fc605@xxxxxxxxxxxxxxxxxxxxxxxxx
    Link: https://syzkaller.appspot.com/bug?id=cabffad18eb74197f84871802fd2c5117b61febf
    Signed-off-by: Brooke Basile <brookebasile@xxxxxxxxx>
    Signed-off-by: Kalle Valo <kvalo@xxxxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20200911071427.32354-1-brookebasile@xxxxxxxxx
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/net/wireless/ath/ath9k/hif_usb.c b/drivers/net/wireless/ath/ath9k/hif_usb.c
index 3f563e02d17da..2ed98aaed6fb5 100644
--- a/drivers/net/wireless/ath/ath9k/hif_usb.c
+++ b/drivers/net/wireless/ath/ath9k/hif_usb.c
@@ -449,10 +449,19 @@ static void hif_usb_stop(void *hif_handle)
 	spin_unlock_irqrestore(&hif_dev->tx.tx_lock, flags);
 
 	/* The pending URBs have to be canceled. */
+	spin_lock_irqsave(&hif_dev->tx.tx_lock, flags);
 	list_for_each_entry_safe(tx_buf, tx_buf_tmp,
 				 &hif_dev->tx.tx_pending, list) {
+		usb_get_urb(tx_buf->urb);
+		spin_unlock_irqrestore(&hif_dev->tx.tx_lock, flags);
 		usb_kill_urb(tx_buf->urb);
+		list_del(&tx_buf->list);
+		usb_free_urb(tx_buf->urb);
+		kfree(tx_buf->buf);
+		kfree(tx_buf);
+		spin_lock_irqsave(&hif_dev->tx.tx_lock, flags);
 	}
+	spin_unlock_irqrestore(&hif_dev->tx.tx_lock, flags);
 
 	usb_kill_anchored_urbs(&hif_dev->mgmt_submitted);
 }
@@ -762,27 +771,37 @@ static void ath9k_hif_usb_dealloc_tx_urbs(struct hif_device_usb *hif_dev)
 	struct tx_buf *tx_buf = NULL, *tx_buf_tmp = NULL;
 	unsigned long flags;
 
+	spin_lock_irqsave(&hif_dev->tx.tx_lock, flags);
 	list_for_each_entry_safe(tx_buf, tx_buf_tmp,
 				 &hif_dev->tx.tx_buf, list) {
+		usb_get_urb(tx_buf->urb);
+		spin_unlock_irqrestore(&hif_dev->tx.tx_lock, flags);
 		usb_kill_urb(tx_buf->urb);
 		list_del(&tx_buf->list);
 		usb_free_urb(tx_buf->urb);
 		kfree(tx_buf->buf);
 		kfree(tx_buf);
+		spin_lock_irqsave(&hif_dev->tx.tx_lock, flags);
 	}
+	spin_unlock_irqrestore(&hif_dev->tx.tx_lock, flags);
 
 	spin_lock_irqsave(&hif_dev->tx.tx_lock, flags);
 	hif_dev->tx.flags |= HIF_USB_TX_FLUSH;
 	spin_unlock_irqrestore(&hif_dev->tx.tx_lock, flags);
 
+	spin_lock_irqsave(&hif_dev->tx.tx_lock, flags);
 	list_for_each_entry_safe(tx_buf, tx_buf_tmp,
 				 &hif_dev->tx.tx_pending, list) {
+		usb_get_urb(tx_buf->urb);
+		spin_unlock_irqrestore(&hif_dev->tx.tx_lock, flags);
 		usb_kill_urb(tx_buf->urb);
 		list_del(&tx_buf->list);
 		usb_free_urb(tx_buf->urb);
 		kfree(tx_buf->buf);
 		kfree(tx_buf);
+		spin_lock_irqsave(&hif_dev->tx.tx_lock, flags);
 	}
+	spin_unlock_irqrestore(&hif_dev->tx.tx_lock, flags);
 
 	usb_kill_anchored_urbs(&hif_dev->mgmt_submitted);
 }