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@jcline.org Cc: Oleksii Kurochko olkuroch@cisco.com Cc: stable@vger.kernel.org # v4.16+ Reported-by: Oleksii Kurochko olkuroch@cisco.com 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@oracle.com
---
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) {