netdev - [PATCH] Bluetooth: Fix double free in hci_conn

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Date:   Thu,  9 Mar 2023 15:46:45 +0800
From:   ZhengHan Wang <wzhmmmmm@...il.com>
To:     marcel@...tmann.org, johan.hedberg@...il.com, luiz.dentz@...il.com
Cc:     linux-bluetooth@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, ZhengHan Wang <wzhmmmmm@...il.com>
Subject: [PATCH] Bluetooth: Fix double free in hci_conn_cleanup

syzbot reports a slab use-after-free in hci_conn_hash_flush [1].
After releasing an object using hci_conn_del_sysfs in the 
hci_conn_cleanup function, releasing the same object again 
using the hci_dev_put and hci_conn_put functions causes a double free.
Here's a simplified flow:

hci_conn_del_sysfs:
  hci_dev_put
    put_device
      kobject_put
        kref_put
          kobject_release
            kobject_cleanup
              kfree_const
                kfree(name)

hci_dev_put:
  ...
    kfree(name)

hci_conn_put:
  put_device
    ...
      kfree(name)

This patch drop the hci_dev_put and hci_conn_put function 
call in hci_conn_cleanup function, because the object is 
freed in hci_conn_del_sysfs function.

Link: https://syzkaller.appspot.com/bug?id=1bb51491ca5df96a5f724899d1dbb87afda61419 [1]

Signed-off-by: ZhengHan Wang <wzhmmmmm@...il.com>
---
 net/bluetooth/hci_conn.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
index acf563fbdfd9..a0ccbef34bc2 100644
--- a/net/bluetooth/hci_conn.c
+++ b/net/bluetooth/hci_conn.c
@@ -152,10 +152,6 @@ static void hci_conn_cleanup(struct hci_conn *conn)
 	hci_conn_del_sysfs(conn);
 
 	debugfs_remove_recursive(conn->debugfs);
-
-	hci_dev_put(hdev);
-
-	hci_conn_put(conn);
 }
 
 static void le_scan_cleanup(struct work_struct *work)
-- 
2.25.1