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.

Since nobody knows what "policy" means, rename the field to "read_only" for clarity.

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

---

v3: - Drop ?: since gcc complains about mixing int and bool (zeroday) - Drop EXPORT_SYMBOL (hch) - s/policy/read_only/ and make it a boolean

v2: - Track user read-only state in a bitmap

- Work around the regression that caused us to drop user preferences on revalidate --- block/blk-core.c | 2 +- block/genhd.c | 34 ++++++++++++++++++++++++---------- block/ioctl.c | 4 ++++ block/partition-generic.c | 7 +++++-- drivers/scsi/sd.c | 4 +--- include/linux/genhd.h | 11 +++++++---- 6 files changed, 42 insertions(+), 20 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c index 4673ebe42255..932f179a9095 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -792,7 +792,7 @@ static inline bool bio_check_ro(struct bio *bio, struct hd_struct *part) { const int op = bio_op(bio);

- if (part->policy && op_is_write(op)) { + if (part->read_only && op_is_write(op)) { char b[BDEVNAME_SIZE];

if (op_is_flush(bio->bi_opf) && !bio_sectors(bio)) diff --git a/block/genhd.c b/block/genhd.c index 703267865f14..9f3a93ca1851 100644 --- a/block/genhd.c +++ b/block/genhd.c @@ -1539,26 +1539,40 @@ static void set_disk_ro_uevent(struct gendisk *gd, int ro) kobject_uevent_env(&disk_to_dev(gd)->kobj, KOBJ_CHANGE, envp); }

-void set_device_ro(struct block_device *bdev, int flag) +void set_device_ro(struct block_device *bdev, bool state) { - bdev->bd_part->policy = flag; + bdev->bd_part->read_only = state; }

EXPORT_SYMBOL(set_device_ro);

-void set_disk_ro(struct gendisk *disk, int flag) +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; +} + +void set_disk_ro(struct gendisk *disk, bool state) { struct disk_part_iter piter; struct hd_struct *part;

- if (disk->part0.policy != flag) { - set_disk_ro_uevent(disk, flag); - disk->part0.policy = flag; - } + if (disk->part0.read_only != state) + set_disk_ro_uevent(disk, state);

- 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; + if (get_user_ro(disk, part->partno)) + part->read_only = true; + else + part->read_only = state; disk_part_iter_exit(&piter); }

@@ -1568,7 +1582,7 @@ int bdev_read_only(struct block_device *bdev) { if (!bdev) return 0; - return bdev->bd_part->policy; + return bdev->bd_part->read_only; }

EXPORT_SYMBOL(bdev_read_only); 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..2bade849cc5c 100644 --- a/block/partition-generic.c +++ b/block/partition-generic.c @@ -98,7 +98,7 @@ static ssize_t part_ro_show(struct device *dev, struct device_attribute *attr, char *buf) { struct hd_struct *p = dev_to_part(dev); - return sprintf(buf, "%d\n", p->policy ? 1 : 0); + return sprintf(buf, "%u\n", p->read_only ? 1 : 0); }

static ssize_t part_alignment_offset_show(struct device *dev, @@ -338,7 +338,10 @@ 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); + if (get_user_ro(disk, partno)) + p->read_only = true; + else + p->read_only = 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 251db30d0882..9d8e15d03d2b 100644 --- a/drivers/scsi/sd.c +++ b/drivers/scsi/sd.c @@ -2608,10 +2608,8 @@ 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; @@ -2649,7 +2647,7 @@ 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..1abde0e88ccb 100644 --- a/include/linux/genhd.h +++ b/include/linux/genhd.h @@ -118,7 +118,8 @@ struct hd_struct { unsigned int discard_alignment; struct device __dev; struct kobject *holder_dir; - int policy, partno; + bool read_only; + int partno; struct partition_meta_info *info; #ifdef CONFIG_FAIL_MAKE_REQUEST int make_it_fail; @@ -194,6 +195,7 @@ 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; @@ -431,12 +433,13 @@ extern void del_gendisk(struct gendisk *gp); extern struct gendisk *get_gendisk(dev_t dev, int *partno); 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 void set_device_ro(struct block_device *bdev, bool state); +extern void set_disk_ro(struct gendisk *disk, bool state); +extern bool get_user_ro(struct gendisk *disk, unsigned int partno);

static inline int get_disk_ro(struct gendisk *disk) { - return disk->part0.policy; + return disk->part0.read_only; }

extern void disk_block_events(struct gendisk *disk);