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scsi: sd: Keep disk read-only when re-reading partition 

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>
This commit is contained in:
Jeremy Cline 2018-03-06 21:47:32 +00:00 committed by Martin K. Petersen
parent 6a2cf8d366
commit 20bd1d026a
1 changed files with 2 additions and 1 deletions
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3
drivers/scsi/sd.c
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@ -2624,6 +2624,7 @@ sd_read_write_protect_flag(struct scsi_disk *sdkp, unsigned char *buffer)
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);
@ -2664,7 +2665,7 @@ sd_read_write_protect_flag(struct scsi_disk *sdkp, unsigned char *buffer)
"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");