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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , linux-kernel@vger.kernel.org, Shihuang Liu , stable@vger.kernel.org Subject: [PATCH REPOST net] amt: fix use-after-free in AMT delayed works Date: Wed, 22 Jul 2026 19:39:19 +0800 Message-ID: <20260722113919.7723-1-shlomojune6@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 Reviewed-by: Simon Horman --- Repost: - Explicitly target the net tree. - Add Reviewed-by from Simon Horman. Previous submission: https://lore.kernel.org/netdev/20260714072705.129262-1-shlomojune6@gmail.com/ drivers/net/amt.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/drivers/net/amt.c b/drivers/net/amt.c index 951dd10e192b..7eb871b9b7e1 100644 --- a/drivers/net/amt.c +++ b/drivers/net/amt.c @@ -2995,9 +2995,15 @@ 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; @@ -3023,8 +3029,8 @@ 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 */ @@ -3278,6 +3284,8 @@ 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: base-commit: ba712ecfd942b68b21a4b0a5daaf72f6616cc66d -- 2.43.0