linux-kernel - Re: [PATCH v4 2/2] scsi: ufs: Protect PM ops and err

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Message-ID: <b32a2064-4ff9-509c-cdaf-434264837917@intel.com>
Date:   Wed, 13 Jan 2021 16:53:28 +0200
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Can Guo <cang@...eaurora.org>, asutoshd@...eaurora.org,
        nguyenb@...eaurora.org, hongwus@...eaurora.org,
        rnayak@...eaurora.org, linux-scsi@...r.kernel.org,
        kernel-team@...roid.com, saravanak@...gle.com, salyzyn@...gle.com
Cc:     Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Stanley Chu <stanley.chu@...iatek.com>,
        Bean Huo <beanhuo@...ron.com>,
        Nitin Rawat <nitirawa@...eaurora.org>,
        Satya Tangirala <satyat@...gle.com>,
        open list <linux-kernel@...r.kernel.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>
Subject: Re: [PATCH v4 2/2] scsi: ufs: Protect PM ops and err_handler from
 user access through sysfs

On 13/01/21 3:57 pm, Can Guo wrote:
> User layer may access sysfs nodes when system PM ops or error handling
> is running, which can cause various problems. Rename eh_sem to host_sem
> and use it to protect PM ops and error handling from user layer intervene.
> 
> Acked-by: Avri Altman <avri.altman@....com>
> Reviewed-by: Stanley Chu <stanley.chu@...iatek.com>
> Signed-off-by: Can Guo <cang@...eaurora.org>
> ---
>  drivers/scsi/ufs/ufs-sysfs.c | 106 ++++++++++++++++++++++++++++++++++++-------
>  drivers/scsi/ufs/ufshcd.c    |  42 ++++++++++-------
>  drivers/scsi/ufs/ufshcd.h    |  10 +++-
>  3 files changed, 125 insertions(+), 33 deletions(-)
> 
> diff --git a/drivers/scsi/ufs/ufs-sysfs.c b/drivers/scsi/ufs/ufs-sysfs.c
> index 0e14384..7cafffc 100644
> --- a/drivers/scsi/ufs/ufs-sysfs.c
> +++ b/drivers/scsi/ufs/ufs-sysfs.c
> @@ -154,18 +154,29 @@ static ssize_t auto_hibern8_show(struct device *dev,
>  				 struct device_attribute *attr, char *buf)
>  {
>  	u32 ahit;
> +	int ret;
>  	struct ufs_hba *hba = dev_get_drvdata(dev);
>  
>  	if (!ufshcd_is_auto_hibern8_supported(hba))
>  		return -EOPNOTSUPP;
>  
> +	down(&hba->host_sem);
> +	if (!ufshcd_is_sysfs_allowed(hba)) {

I expect debugfs has the same potential problem, so maybe
ufshcd_is_sysfs_allowed() is not quite the right name.

> +		ret = -EBUSY;
> +		goto out;
> +	}
> +