amt: fix use-after-free in AMT delayed works

When an AMT device is removed, pending delayed works can still access
the freed amt_dev structure, which may result in kernel crashes or
memory corruption.

amt_dev_stop() cancels req_wq and discovery_wq with
cancel_delayed_work_sync(), but these works can be scheduled again
from event_wq after the cancellation. This allows delayed works to
access the freed amt_dev structure after the netdev has been released.

The following is a simple race scenario:

CPU0                         CPU1

amt_dev_stop()
cancel_delayed_work_sync()
                             amt_event_work()
                             mod_delayed_work(req_wq)
free netdev
                             req_wq accesses freed amt_dev

Use disable_delayed_work_sync() in amt_dev_stop() to prevent req_wq and
discovery_wq from being queued again and wait for running work items
to complete.

The delayed works are disabled after initialization in
amt_newlink() and enabled only when the device is successfully opened.
This keeps the delayed work lifecycle synchronized with the lifetime
of the AMT device.

Fixes: cbc21dc1cfe9 ("amt: add data plane of amt interface")
Cc: stable@vger.kernel.org
Signed-off-by: Shihuang Liu <shlomojune6@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Taehee Yoo <ap420073@gmail.com>
Link: https://patch.msgid.link/20260722113919.7723-1-shlomojune6@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/amt.c b/drivers/net/amt.c
index b733309b866ffa35f6da0f8749922d40640a9b1c..182a41d59a75d836585e197f9edda64d0b706036 100644 (file)
--- a/drivers/net/amt.c
+++ b/drivers/net/amt.c
@@ -3034,9 +3034,15 @@ static int amt_dev_open(struct net_device *dev)
        amt->event_idx = 0;
        amt->nr_events = 0;
 
+       enable_delayed_work(&amt->discovery_wq);
+       enable_delayed_work(&amt->req_wq);
+
        err = amt_socket_create(amt);
-       if (err)
+       if (err) {
+               disable_delayed_work(&amt->req_wq);
+               disable_delayed_work(&amt->discovery_wq);
                return err;
+       }
 
        amt->req_cnt = 0;
        amt->remote_ip = 0;
@@ -3062,8 +3068,8 @@ static int amt_dev_stop(struct net_device *dev)
        struct sock *sk;
        int i;
 
-       cancel_delayed_work_sync(&amt->req_wq);
-       cancel_delayed_work_sync(&amt->discovery_wq);
+       disable_delayed_work_sync(&amt->req_wq);
+       disable_delayed_work_sync(&amt->discovery_wq);
        cancel_delayed_work_sync(&amt->secret_wq);
 
        /* shutdown */
@@ -3317,6 +3323,8 @@ static int amt_newlink(struct net_device *dev,
        INIT_DELAYED_WORK(&amt->req_wq, amt_req_work);
        INIT_DELAYED_WORK(&amt->secret_wq, amt_secret_work);
        INIT_WORK(&amt->event_wq, amt_event_work);
+       disable_delayed_work(&amt->req_wq);
+       disable_delayed_work(&amt->discovery_wq);
        INIT_LIST_HEAD(&amt->tunnel_list);
        return 0;
 err: