linux-kernel - Re: [PATCH V6] brd: check and limit max

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Date:   Tue, 4 Feb 2020 07:19:45 -0700
From:   Jens Axboe <axboe@...nel.dk>
To:     Zhiqiang Liu <liuzhiqiang26@...wei.com>,
        Ming Lei <ming.lei@...hat.com>
Cc:     linux-block@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Mingfangsen <mingfangsen@...wei.com>,
        Yanxiaodan <yanxiaodan@...wei.com>, Guiyao <guiyao@...wei.com>,
        "wubo (T)" <wubo40@...wei.com>
Subject: Re: [PATCH V6] brd: check and limit max_part par

On 2/4/20 4:30 AM, Zhiqiang Liu wrote:
> In brd_init func, rd_nr num of brd_device are firstly allocated
> and add in brd_devices, then brd_devices are traversed to add each
> brd_device by calling add_disk func. When allocating brd_device,
> the disk->first_minor is set to i * max_part, if rd_nr * max_part
> is larger than MINORMASK, two different brd_device may have the same
> devt, then only one of them can be successfully added.
> when rmmod brd.ko, it will cause oops when calling brd_exit.
> 
> Follow those steps:
>   # modprobe brd rd_nr=3 rd_size=102400 max_part=1048576
>   # rmmod brd
> then, the oops will appear.
> 
> Oops log:
> [  726.613722] Call trace:
> [  726.614175]  kernfs_find_ns+0x24/0x130
> [  726.614852]  kernfs_find_and_get_ns+0x44/0x68
> [  726.615749]  sysfs_remove_group+0x38/0xb0
> [  726.616520]  blk_trace_remove_sysfs+0x1c/0x28
> [  726.617320]  blk_unregister_queue+0x98/0x100
> [  726.618105]  del_gendisk+0x144/0x2b8
> [  726.618759]  brd_exit+0x68/0x560 [brd]
> [  726.619501]  __arm64_sys_delete_module+0x19c/0x2a0
> [  726.620384]  el0_svc_common+0x78/0x130
> [  726.621057]  el0_svc_handler+0x38/0x78
> [  726.621738]  el0_svc+0x8/0xc
> [  726.622259] Code: aa0203f6 aa0103f7 aa1e03e0 d503201f (7940e260)
> 
> Here, we add brd_check_and_reset_par func to check and limit max_part par.

Applied, thanks.

-- 
Jens Axboe