linux-kernel - Re: [PATCH v2] ublk_drv: fix NULL pointer dereference in ublk_ctrl_start

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Message-ID: <e4a4a9a2-a7a7-67e6-a2ca-31f016fd3e2e@huaweicloud.com>
Date: Mon, 8 Jul 2024 21:14:45 +0800
From: Li Nan <linan666@...weicloud.com>
To: linan666@...weicloud.com, axboe@...nel.dk
Cc: czhong@...hat.com, linux-block@...r.kernel.org,
 linux-kernel@...r.kernel.org, yukuai3@...wei.com, yi.zhang@...wei.com,
 houtao1@...wei.com, yangerkun@...wei.com
Subject: Re: [PATCH v2] ublk_drv: fix NULL pointer dereference in
 ublk_ctrl_start_recovery()

friendly ping...

在 2024/6/3 14:53, linan666@...weicloud.com 写道:
> From: Li Nan <linan122@...wei.com>
> 
> When two UBLK_CMD_START_USER_RECOVERY commands are submitted, the
> first one sets 'ubq->ubq_daemon' to NULL, and the second one triggers
> WARN in ublk_queue_reinit() and subsequently a NULL pointer dereference
> issue.
> 
> Fix it by adding the check in ublk_ctrl_start_recovery() and return
> immediately in case of zero 'ub->nr_queues_ready'.
> 
>    BUG: kernel NULL pointer dereference, address: 0000000000000028
>    RIP: 0010:ublk_ctrl_start_recovery.constprop.0+0x82/0x180
>    Call Trace:
>     <TASK>
>     ? __die+0x20/0x70
>     ? page_fault_oops+0x75/0x170
>     ? exc_page_fault+0x64/0x140
>     ? asm_exc_page_fault+0x22/0x30
>     ? ublk_ctrl_start_recovery.constprop.0+0x82/0x180
>     ublk_ctrl_uring_cmd+0x4f7/0x6c0
>     ? pick_next_task_idle+0x26/0x40
>     io_uring_cmd+0x9a/0x1b0
>     io_issue_sqe+0x193/0x3f0
>     io_wq_submit_work+0x9b/0x390
>     io_worker_handle_work+0x165/0x360
>     io_wq_worker+0xcb/0x2f0
>     ? finish_task_switch.isra.0+0x203/0x290
>     ? finish_task_switch.isra.0+0x203/0x290
>     ? __pfx_io_wq_worker+0x10/0x10
>     ret_from_fork+0x2d/0x50
>     ? __pfx_io_wq_worker+0x10/0x10
>     ret_from_fork_asm+0x1a/0x30
>     </TASK>
> 
> Fixes: c732a852b419 ("ublk_drv: add START_USER_RECOVERY and END_USER_RECOVERY support")
> Reported-and-tested-by: Changhui Zhong <czhong@...hat.com>
> Closes: https://lore.kernel.org/all/CAGVVp+UvLiS+bhNXV-h2icwX1dyybbYHeQUuH7RYqUvMQf6N3w@mail.gmail.com
> Signed-off-by: Li Nan <linan122@...wei.com>
> Reviewed-by: Ming Lei <ming.lei@...hat.com>
> ---
> v2: add the check to ublk_ctrl_start_recovery().
> 
>   drivers/block/ublk_drv.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
> index 4e159948c912..ebd997095b65 100644
> --- a/drivers/block/ublk_drv.c
> +++ b/drivers/block/ublk_drv.c
> @@ -2661,6 +2661,8 @@ static int ublk_ctrl_start_recovery(struct ublk_device *ub,
>   	mutex_lock(&ub->mutex);
>   	if (!ublk_can_use_recovery(ub))
>   		goto out_unlock;
> +	if (!ub->nr_queues_ready)
> +		goto out_unlock;
>   	/*
>   	 * START_RECOVERY is only allowd after:
>   	 *

-- 
Thanks,
Nan