linux-kernel - [PATCH] wireless: ath9k: hif_usb: fix race condition between usb_get_urb() and usb_kill_anchored

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Date:   Fri, 11 Sep 2020 03:14:27 -0400
From:   Brooke Basile <brookebasile@...il.com>
To:     kvalo@...eaurora.org, davem@...emloft.net, kuba@...nel.org
Cc:     gregkh@...uxfoundation.org, linux-wireless@...r.kernel.org,
        linux-kernel@...r.kernel.org, ath9k-devel@....qualcomm.com,
        syzkaller-bugs@...glegroups.com,
        Brooke Basile <brookebasile@...il.com>,
        syzbot+89bd486af9427a9fc605@...kaller.appspotmail.com
Subject: [PATCH] wireless: ath9k: hif_usb: fix race condition between usb_get_urb() and usb_kill_anchored_urbs()

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@...kaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?id=cabffad18eb74197f84871802fd2c5117b61febf
Signed-off-by: Brooke Basile <brookebasile@...il.com>
---
 drivers/net/wireless/ath/ath9k/hif_usb.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/net/wireless/ath/ath9k/hif_usb.c b/drivers/net/wireless/ath/ath9k/hif_usb.c
index 3f563e02d17d..2ed98aaed6fb 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);
 }
--
2.28.0