linux-kernel - Re: [PATCHv3] thunderbolt: do not double dequeue a request

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Message-ID: <ojkrbtd2kpweo5xcfulfobdavj5ab3ysxxle4kr5oa455me77s@p2o4jdwsr3m2>
Date: Thu, 8 May 2025 12:47:18 +0900
From: Sergey Senozhatsky <senozhatsky@...omium.org>
To: Mika Westerberg <westeri@...nel.org>
Cc: Andreas Noever <andreas.noever@...il.com>, 
	Michael Jamet <michael.jamet@...el.com>, Yehezkel Bernat <YehezkelShB@...il.com>, 
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org, stable@...r.kernel.org, 
	Sergey Senozhatsky <senozhatsky@...omium.org>
Subject: Re: [PATCHv3] thunderbolt: do not double dequeue a request

On (25/03/28 00:03), Sergey Senozhatsky wrote:
> Some of our devices crash in tb_cfg_request_dequeue():
> 
>  general protection fault, probably for non-canonical address 0xdead000000000122
> 
>  CPU: 6 PID: 91007 Comm: kworker/6:2 Tainted: G U W 6.6.65
>  RIP: 0010:tb_cfg_request_dequeue+0x2d/0xa0
>  Call Trace:
>  <TASK>
>  ? tb_cfg_request_dequeue+0x2d/0xa0
>  tb_cfg_request_work+0x33/0x80
>  worker_thread+0x386/0x8f0
>  kthread+0xed/0x110
>  ret_from_fork+0x38/0x50
>  ret_from_fork_asm+0x1b/0x30
> 
> The circumstances are unclear, however, the theory is that
> tb_cfg_request_work() can be scheduled twice for a request:
> first time via frame.callback from ring_work() and second
> time from tb_cfg_request().  Both times kworkers will execute
> tb_cfg_request_dequeue(), which results in double list_del()
> from the ctl->request_queue (the list poison deference hints
> at it: 0xdead000000000122).
> 
> Do not dequeue requests that don't have TB_CFG_REQUEST_ACTIVE
> bit set.

Mika, as was discussed in [1] thread we rolled out the fix to
our fleet and we don't see the crashes anymore.  So it's tested
and verified.

[1] https://lore.kernel.org/linux-kernel/20250327145543.GC3152277@black.fi.intel.com

> ---
> 
> v3: tweaked commit message
> 
>  drivers/thunderbolt/ctl.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/thunderbolt/ctl.c b/drivers/thunderbolt/ctl.c
> index cd15e84c47f4..1db2e951b53f 100644
> --- a/drivers/thunderbolt/ctl.c
> +++ b/drivers/thunderbolt/ctl.c
> @@ -151,6 +151,11 @@ static void tb_cfg_request_dequeue(struct tb_cfg_request *req)
>  	struct tb_ctl *ctl = req->ctl;
>  
>  	mutex_lock(&ctl->request_queue_lock);
> +	if (!test_bit(TB_CFG_REQUEST_ACTIVE, &req->flags)) {
> +		mutex_unlock(&ctl->request_queue_lock);
> +		return;
> +	}
> +
>  	list_del(&req->list);
>  	clear_bit(TB_CFG_REQUEST_ACTIVE, &req->flags);
>  	if (test_bit(TB_CFG_REQUEST_CANCELED, &req->flags))
> -- 
> 2.49.0.395.g12beb8f557-goog
>