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

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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: cbc21dc1cf ("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>
This commit is contained in:
Shihuang Liu 2026-07-22 19:39:19 +08:00 committed by Jakub Kicinski
parent 249447ff83
commit ea20c44935
1 changed files with 11 additions and 3 deletions
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14
drivers/net/amt.c
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@ -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: