Re: [PATCH v4 2/2] scsi: ufs: Protect PM ops and err_handler from user access through sysfs

From: Adrian Hunter <adrian.hunter@intel.com>
To: Can Guo <cang@codeaurora.org>,
	asutoshd@codeaurora.org, nguyenb@codeaurora.org,
	hongwus@codeaurora.org, rnayak@codeaurora.org,
	linux-scsi@vger.kernel.org, kernel-team@android.com,
	saravanak@google.com, salyzyn@google.com
Cc: Alim Akhtar <alim.akhtar@samsung.com>,
	Avri Altman <avri.altman@wdc.com>,
	"James E.J. Bottomley" <jejb@linux.ibm.com>,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	Matthias Brugger <matthias.bgg@gmail.com>,
	Stanley Chu <stanley.chu@mediatek.com>,
	Bean Huo <beanhuo@micron.com>,
	Nitin Rawat <nitirawa@codeaurora.org>,
	Satya Tangirala <satyat@google.com>,
	open list <linux-kernel@vger.kernel.org>,
	"moderated list:ARM/Mediatek SoC support" 
	<linux-arm-kernel@lists.infradead.org>,
	"moderated list:ARM/Mediatek SoC support" 
	<linux-mediatek@lists.infradead.org>
Subject: Re: [PATCH v4 2/2] scsi: ufs: Protect PM ops and err_handler from user access through sysfs
Date: Wed, 13 Jan 2021 16:53:28 +0200	[thread overview]
Message-ID: <b32a2064-4ff9-509c-cdaf-434264837917@intel.com> (raw)
In-Reply-To: <1610546230-14732-3-git-send-email-cang@codeaurora.org>

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@wdc.com>
> Reviewed-by: Stanley Chu <stanley.chu@mediatek.com>
> Signed-off-by: Can Guo <cang@codeaurora.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;
> +	}
> +