linux-kernel - [PATCH v3] bluetooth: hci_h5: fix memory leak in h5

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Message-Id: <20201004051708.21985-1-anant.thazhemadam@gmail.com>
Date:   Sun,  4 Oct 2020 10:47:08 +0530
From:   Anant Thazhemadam <anant.thazhemadam@...il.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     linux-kernel-mentees@...ts.linuxfoundation.org,
        Anant Thazhemadam <anant.thazhemadam@...il.com>,
        syzbot+6ce141c55b2f7aafd1c4@...kaller.appspotmail.com,
        Marcel Holtmann <marcel@...tmann.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        Hans de Goede <hdegoede@...hat.com>,
        linux-bluetooth@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v3] bluetooth: hci_h5: fix memory leak in h5_close

When h5_close() is called and !hu->serdev, h5 is directly freed.
However, h5->rx_skb is not freed before h5 is freed, which causes
a memory leak.
Freeing h5->rx_skb (when !hu->serdev) fixes this memory leak before
freeing h5.

Fixes: ce945552fde4 ("Bluetooth: hci_h5: Add support for serdev enumerated devices")
Reported-by: syzbot+6ce141c55b2f7aafd1c4@...kaller.appspotmail.com
Tested-by: syzbot+6ce141c55b2f7aafd1c4@...kaller.appspotmail.com
Signed-off-by: Anant Thazhemadam <anant.thazhemadam@...il.com>
---
Changes in v3:
	* Free h5->rx_skb when !hu->serdev, and fix the memory leak
	* Do not incorrectly and unnecessarily call serdev_device_close()

Changes in v2:
	* Fixed the Fixes tag

Hans de Goede also suggested calling h5_reset_rx() on close (for both, !hu->serdev
and hu->serdev cases). 
However, doing so seems to lead to a null-ptr-dereference error,
        https://syzkaller.appspot.com/text?tag=CrashReport&x=136a9a5d900000,
and for this reason, it has not been implemented.

Instead, directly freeing h5->rx_skb seems to suffice in preventing the memory leak
reported. 
And since h5 is freed immediately after freeing h5->rx_skb, assigning h5->rx_skb to
be NULL isn't necessary.

 drivers/bluetooth/hci_h5.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/bluetooth/hci_h5.c b/drivers/bluetooth/hci_h5.c
index e41854e0d79a..171e55c080ce 100644
--- a/drivers/bluetooth/hci_h5.c
+++ b/drivers/bluetooth/hci_h5.c
@@ -248,8 +248,10 @@ static int h5_close(struct hci_uart *hu)
 	if (h5->vnd && h5->vnd->close)
 		h5->vnd->close(h5);
 
-	if (!hu->serdev)
+	if (!hu->serdev){
+		kfree_skb(h5->rx_skb);
 		kfree(h5);
+	}
 
 	return 0;
 }
-- 
2.25.1