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

On 2021-01-13 22:53, Adrian Hunter wrote:

On 13/01/21 3:57 pm, Can Guo wrote:

quoted

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 <redacted>
Signed-off-by: Can Guo <redacted>
---
 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.

I noticed your debugfs change - currently it is only printing
error counts recorded in hba struct, which is fine.
Even in this patch, the check is only added for those entries
which need to talk with HW. Sysfs nodes like show/store rpm/spm_lvl
does not need this check.

Thanks,
Can Guo.

quoted

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

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