Some devices come online in write protected state and switch to
read-write once they are ready to process I/O requests. These devices
broke with commit 20bd1d026aac ("scsi: sd: Keep disk read-only when
re-reading partition") because we had no way to distinguish between a
user decision to set a block_device read-only and the actual hardware
device being write-protected.
Because partitions are dropped and recreated on revalidate we are
unable to persist any user-provided policy in hd_struct. Introduce a
bitmap in struct gendisk to track the user configuration. This bitmap
is updated when BLKROSET is called on a given disk or partition.
A helper function, get_user_ro(), is provided to determine whether the
ioctl has forced read-only state for a given block device. This helper
is used by set_disk_ro() and add_partition() to ensure that both
existing and newly created partitions will get the correct state.
- If BLKROSET sets a whole disk device read-only, all partitions will
now end up in a read-only state.
- If BLKROSET sets a given partition read-only, that partition will
remain read-only post revalidate.
- Otherwise both the whole disk device and any partitions will
reflect the write protect state of the underlying device.
Cc: Jeremy Cline <jeremy@xxxxxxxxxx>
Cc: Oleksii Kurochko <olkuroch@xxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # v4.16+
Reported-by: Oleksii Kurochko <olkuroch@xxxxxxxxx>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=201221
Fixes: 20bd1d026aac ("scsi: sd: Keep disk read-only when re-reading partition")
Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
---
v2:
- Track user read-only state in a bitmap
- Work around the regression that caused us to drop user
preferences on revalidate
---
block/genhd.c | 22 +++++++++++++++++-----
block/ioctl.c | 4 ++++
block/partition-generic.c | 2 +-
drivers/scsi/sd.c | 4 +---
include/linux/genhd.h | 2 ++
5 files changed, 25 insertions(+), 9 deletions(-)
diff --git a/block/genhd.c b/block/genhd.c
index 1dd8fd6613b8..34667eb1d3cc 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -1544,19 +1544,31 @@ void set_device_ro(struct block_device *bdev, int flag)
EXPORT_SYMBOL(set_device_ro);
+bool get_user_ro(struct gendisk *disk, unsigned int partno)
+{
+ /* Is the user read-only bit set for the whole disk device? */
+ if (test_bit(0, disk->user_ro_bitmap))
+ return true;
+
+ /* Is the user read-only bit set for this particular partition? */
+ if (test_bit(partno, disk->user_ro_bitmap))
+ return true;
+
+ return false;
+}
+EXPORT_SYMBOL(get_user_ro);
+
void set_disk_ro(struct gendisk *disk, int flag)
{
struct disk_part_iter piter;
struct hd_struct *part;
- if (disk->part0.policy != flag) {
+ if (disk->part0.policy != flag)
set_disk_ro_uevent(disk, flag);
- disk->part0.policy = flag;
- }
- disk_part_iter_init(&piter, disk, DISK_PITER_INCL_EMPTY);
+ disk_part_iter_init(&piter, disk, DISK_PITER_INCL_EMPTY_PART0);
while ((part = disk_part_iter_next(&piter)))
- part->policy = flag;
+ part->policy = get_user_ro(disk, part->partno) ?: flag;
disk_part_iter_exit(&piter);
}
diff --git a/block/ioctl.c b/block/ioctl.c
index 4825c78a6baa..41206df89485 100644
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -451,6 +451,10 @@ static int blkdev_roset(struct block_device *bdev, fmode_t mode,
return ret;
if (get_user(n, (int __user *)arg))
return -EFAULT;
+ if (n)
+ set_bit(bdev->bd_partno, bdev->bd_disk->user_ro_bitmap);
+ else
+ clear_bit(bdev->bd_partno, bdev->bd_disk->user_ro_bitmap);
set_device_ro(bdev, n);
return 0;
}
diff --git a/block/partition-generic.c b/block/partition-generic.c
index 8e596a8dff32..c6a3c21c2496 100644
--- a/block/partition-generic.c
+++ b/block/partition-generic.c
@@ -338,7 +338,7 @@ struct hd_struct *add_partition(struct gendisk *disk, int partno,
queue_limit_discard_alignment(&disk->queue->limits, start);
p->nr_sects = len;
p->partno = partno;
- p->policy = get_disk_ro(disk);
+ p->policy = get_user_ro(disk, partno) ?: get_disk_ro(disk);
if (info) {
struct partition_meta_info *pinfo = alloc_part_info(disk);
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 67cc439b86e4..5dfe37b08d3b 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -2591,10 +2591,8 @@ 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);
if (sdp->skip_ms_page_3f) {
sd_first_printk(KERN_NOTICE, sdkp, "Assuming Write Enabled\n");
return;
@@ -2632,7 +2630,7 @@ 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 || disk_ro);
+ set_disk_ro(sdkp->disk, sdkp->write_prot);
if (sdkp->first_scan || old_wp != sdkp->write_prot) {
sd_printk(KERN_NOTICE, sdkp, "Write Protect is %s\n",
sdkp->write_prot ? "on" : "off");
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 06c0fd594097..9645c2604465 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -194,6 +194,7 @@ struct gendisk {
*/
struct disk_part_tbl __rcu *part_tbl;
struct hd_struct part0;
+ DECLARE_BITMAP(user_ro_bitmap, DISK_MAX_PARTS);
const struct block_device_operations *fops;
struct request_queue *queue;
@@ -433,6 +434,7 @@ extern struct block_device *bdget_disk(struct gendisk *disk, int partno);
extern void set_device_ro(struct block_device *bdev, int flag);
extern void set_disk_ro(struct gendisk *disk, int flag);
+extern bool get_user_ro(struct gendisk *disk, unsigned int partno);
static inline int get_disk_ro(struct gendisk *disk)
{
--
2.19.2
