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Subject[PATCH 4.4 128/268] scsi: sd: Keep disk read-only when re-reading partition
Date
4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jeremy Cline <jeremy@jcline.org>

[ Upstream commit 20bd1d026aacc5399464f8328f305985c493cde3 ]

If the read-only flag is true on a SCSI disk, re-reading the partition
table sets the flag back to false.

To observe this bug, you can run:

1. blockdev --setro /dev/sda
2. blockdev --rereadpt /dev/sda
3. blockdev --getro /dev/sda

This commit reads the disk's old state and combines it with the device
disk-reported state rather than unconditionally marking it as RW.

Reported-by: Li Ning <lining916740672@icloud.com>
Signed-off-by: Jeremy Cline <jeremy@jcline.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/scsi/sd.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -2395,6 +2395,7 @@ sd_read_write_protect_flag(struct scsi_d
int res;
struct scsi_device *sdp = sdkp->device;
struct scsi_mode_data data;
+ int disk_ro = get_disk_ro(sdkp->disk);
int old_wp = sdkp->write_prot;

set_disk_ro(sdkp->disk, 0);
@@ -2435,7 +2436,7 @@ sd_read_write_protect_flag(struct scsi_d
"Test WP failed, assume Write Enabled\n");
} else {
sdkp->write_prot = ((data.device_specific & 0x80) != 0);
- set_disk_ro(sdkp->disk, sdkp->write_prot);
+ set_disk_ro(sdkp->disk, sdkp->write_prot || disk_ro);
if (sdkp->first_scan || old_wp != sdkp->write_prot) {
sd_printk(KERN_NOTICE, sdkp, "Write Protect is %s\n",
sdkp->write_prot ? "on" : "off");

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