scsi: sd_zbc: Prevent zone information memory leak

Make sure to always free a scsi disk zone information, even for regular
disks. This ensures that there is no memory leak, even in the case of a
zoned disk changing type to a regular disk (e.g. with a reformat using the
FORMAT WITH PRESET command or other vendor proprietary command).

To do this, rename sd_zbc_clear_zone_info() to sd_zbc_free_zone_info() and
remove sd_zbc_release_disk(). A call to sd_zbc_free_zone_info() is added to
sd_zbc_read_zones() for drives for which sd_is_zoned() returns
false. Furthermore, sd_zbc_free_zone_info() code make s sure that the sdkp
rev_mutex is never used while not being initialized by gating the cleanup
code with a a check on the zone_wp_update_buf field as it is never NULL
when rev_mutex has been initialized.

Link: https://lore.kernel.org/r/20220601062544.905141-3-damien.lemoal@opensource.wdc.com
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/sd.c

@@ -3580,7 +3580,7 @@ static void scsi_disk_release(struct device *dev)
 	struct scsi_disk *sdkp = to_scsi_disk(dev);
 
 	ida_free(&sd_index_ida, sdkp->index);
-	sd_zbc_release_disk(sdkp);
+	sd_zbc_free_zone_info(sdkp);
 	put_device(&sdkp->device->sdev_gendev);
 	free_opal_dev(sdkp->opal_dev);
 

drivers/scsi/sd.h

@@ -241,7 +241,7 @@ static inline int sd_is_zoned(struct scsi_disk *sdkp)
 
 #ifdef CONFIG_BLK_DEV_ZONED
 
-void sd_zbc_release_disk(struct scsi_disk *sdkp);
+void sd_zbc_free_zone_info(struct scsi_disk *sdkp);
 int sd_zbc_read_zones(struct scsi_disk *sdkp, u8 buf[SD_BUF_SIZE]);
 int sd_zbc_revalidate_zones(struct scsi_disk *sdkp);
 blk_status_t sd_zbc_setup_zone_mgmt_cmnd(struct scsi_cmnd *cmd,
@@ -256,7 +256,7 @@ blk_status_t sd_zbc_prepare_zone_append(struct scsi_cmnd *cmd, sector_t *lba,
 
 #else /* CONFIG_BLK_DEV_ZONED */
 
-static inline void sd_zbc_release_disk(struct scsi_disk *sdkp) {}
+static inline void sd_zbc_free_zone_info(struct scsi_disk *sdkp) {}
 
 static inline int sd_zbc_read_zones(struct scsi_disk *sdkp, u8 buf[SD_BUF_SIZE])
 {

drivers/scsi/sd_zbc.c

@@ -786,8 +786,11 @@ static int sd_zbc_init_disk(struct scsi_disk *sdkp)
 	return 0;
 }
 
-static void sd_zbc_clear_zone_info(struct scsi_disk *sdkp)
+void sd_zbc_free_zone_info(struct scsi_disk *sdkp)
 {
+	if (!sdkp->zone_wp_update_buf)
+		return;
+
 	/* Serialize against revalidate zones */
 	mutex_lock(&sdkp->rev_mutex);
 
@@ -802,12 +805,6 @@ static void sd_zbc_clear_zone_info(struct scsi_disk *sdkp)
 	mutex_unlock(&sdkp->rev_mutex);
 }
 
-void sd_zbc_release_disk(struct scsi_disk *sdkp)
-{
-	if (sd_is_zoned(sdkp))
-		sd_zbc_clear_zone_info(sdkp);
-}
-
 static void sd_zbc_revalidate_zones_cb(struct gendisk *disk)
 {
 	struct scsi_disk *sdkp = scsi_disk(disk);
@@ -914,12 +911,15 @@ int sd_zbc_read_zones(struct scsi_disk *sdkp, u8 buf[SD_BUF_SIZE])
 	u32 zone_blocks = 0;
 	int ret;
 
-	if (!sd_is_zoned(sdkp))
+	if (!sd_is_zoned(sdkp)) {
 		/*
-		 * Device managed or normal SCSI disk,
-		 * no special handling required
+		 * Device managed or normal SCSI disk, no special handling
+		 * required. Nevertheless, free the disk zone information in
+		 * case the device type changed.
 		 */
+		sd_zbc_free_zone_info(sdkp);
 		return 0;
+	}
 
 	/* READ16/WRITE16 is mandatory for ZBC disks */
 	sdkp->device->use_16_for_rw = 1;
@@ -928,11 +928,11 @@ int sd_zbc_read_zones(struct scsi_disk *sdkp, u8 buf[SD_BUF_SIZE])
 	if (!blk_queue_is_zoned(q)) {
 		/*
 		 * This can happen for a host aware disk with partitions.
-		 * The block device zone information was already cleared
-		 * by blk_queue_set_zoned(). Only clear the scsi disk zone
+		 * The block device zone model was already cleared by
+		 * blk_queue_set_zoned(). Only free the scsi disk zone
 		 * information and exit early.
 		 */
-		sd_zbc_clear_zone_info(sdkp);
+		sd_zbc_free_zone_info(sdkp);
 		return 0;
 	}