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>

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index ab75ebd518a7dc6a9928ba2270b12f3d3169a686..3b45f7fc562017c8f626c46153e343a1f675cdfb 100644 (file)
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -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");