linux-kernel - Re: [PATCH net] cnic: Fix use-after-free bugs in cnic_delete

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Message-ID: <20250915182235.77a556c4@kernel.org>
Date: Mon, 15 Sep 2025 18:22:35 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Duoming Zhou <duoming@....edu.cn>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, pabeni@...hat.com,
 edumazet@...gle.com, davem@...emloft.net, andrew+netdev@...n.ch
Subject: Re: [PATCH net] cnic: Fix use-after-free bugs in cnic_delete_task

On Sun, 14 Sep 2025 11:43:35 +0800 Duoming Zhou wrote:
> The original code uses cancel_delayed_work() in cnic_cm_stop_bnx2x_hw(),
> which does not guarantee that the delayed work item 'delete_task' has
> fully completed if it was already running. Additionally, the delayed work
> item is cyclic, flush_workqueue() in cnic_cm_stop_bnx2x_hw() could not
> prevent the new incoming ones. This leads to use-after-free scenarios
> where the cnic_dev is deallocated by cnic_free_dev(), while delete_task
> remains active and attempt to dereference cnic_dev in cnic_delete_task().

[snip]

> Replace cancel_delayed_work() with cancel_delayed_work_sync() to ensure
> that the delayed work item is properly canceled and any executing delayed
> work has finished before the cnic_dev is deallocated.

Have you tested this on real HW? Please always include information on
how you discovered the problem and whether you managed to test the fix.

> Fixes: fdf24086f475 ("cnic: Defer iscsi connection cleanup")
> Signed-off-by: Duoming Zhou <duoming@....edu.cn>

>  	cnic_bnx2x_delete_wait(dev, 0);
>  
> -	cancel_delayed_work(&cp->delete_task);
> +	cancel_delayed_work_sync(&cp->delete_task);
>  	flush_workqueue(cnic_wq);

AFAICT your patch is a nop, doubt this if fixing anything

>  	if (atomic_read(&cp->iscsi_conn) != 0)
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