On 2020/07/30 20:25, Johannes Thumshirn wrote: > When we loose a device for whatever reason while (re)scanning zones, we > trip over a NULL pointer in blk_revalidate_zone_cb, like in the following > log: > > sd 0:0:0:0: [sda] 3418095616 4096-byte logical blocks: (14.0 TB/12.7 TiB) > sd 0:0:0:0: [sda] 52156 zones of 65536 logical blocks > sd 0:0:0:0: [sda] Write Protect is off > sd 0:0:0:0: [sda] Mode Sense: 37 00 00 08 > sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA > sd 0:0:0:0: [sda] REPORT ZONES start lba 1065287680 failed > sd 0:0:0:0: [sda] REPORT ZONES: Result: hostbyte=0x00 driverbyte=0x08 > sd 0:0:0:0: [sda] Sense Key : 0xb [current] > sd 0:0:0:0: [sda] ASC=0x0 ASCQ=0x6 > sda: failed to revalidate zones > sd 0:0:0:0: [sda] 0 4096-byte logical blocks: (0 B/0 B) > sda: detected capacity change from 14000519643136 to 0 > ================================================================== > BUG: KASAN: null-ptr-deref in blk_revalidate_zone_cb+0x1b7/0x550 > Write of size 8 at addr 0000000000000010 by task kworker/u4:1/58 > > CPU: 1 PID: 58 Comm: kworker/u4:1 Not tainted 5.8.0-rc1 #692 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4-rebuilt.opensuse.org 04/01/2014 > Workqueue: events_unbound async_run_entry_fn > Call Trace: > dump_stack+0x7d/0xb0 > ? blk_revalidate_zone_cb+0x1b7/0x550 > kasan_report.cold+0x5/0x37 > ? blk_revalidate_zone_cb+0x1b7/0x550 > check_memory_region+0x145/0x1a0 > blk_revalidate_zone_cb+0x1b7/0x550 > sd_zbc_parse_report+0x1f1/0x370 > ? blk_req_zone_write_trylock+0x200/0x200 > ? sectors_to_logical+0x60/0x60 > ? blk_req_zone_write_trylock+0x200/0x200 > ? blk_req_zone_write_trylock+0x200/0x200 > sd_zbc_report_zones+0x3c4/0x5e0 > ? sd_dif_config_host+0x500/0x500 > blk_revalidate_disk_zones+0x231/0x44d > ? _raw_write_lock_irqsave+0xb0/0xb0 > ? blk_queue_free_zone_bitmaps+0xd0/0xd0 > sd_zbc_read_zones+0x8cf/0x11a0 > sd_revalidate_disk+0x305c/0x64e0 > ? __device_add_disk+0x776/0xf20 > ? read_capacity_16.part.0+0x1080/0x1080 > ? blk_alloc_devt+0x250/0x250 > ? create_object.isra.0+0x595/0xa20 > ? kasan_unpoison_shadow+0x33/0x40 > sd_probe+0x8dc/0xcd2 > really_probe+0x20e/0xaf0 > __driver_attach_async_helper+0x249/0x2d0 > async_run_entry_fn+0xbe/0x560 > process_one_work+0x764/0x1290 > ? _raw_read_unlock_irqrestore+0x30/0x30 > worker_thread+0x598/0x12f0 > ? __kthread_parkme+0xc6/0x1b0 > ? schedule+0xed/0x2c0 > ? process_one_work+0x1290/0x1290 > kthread+0x36b/0x440 > ? kthread_create_worker_on_cpu+0xa0/0xa0 > ret_from_fork+0x22/0x30 > ================================================================== > > When the device is already gone we end up with the following scenario: > The device's capacity is 0 and thus the number of zones will be 0 as well. When > allocating the bitmap for the conventional zones, we then trip over a NULL > pointer. > > So if we encounter a zoned block device with a 0 capacity, don't dare to > revalidate the zones sizes. > > Signed-off-by: Johannes Thumshirn <johannes.thumshirn@xxxxxxx> > --- > > Note: This is a hot-fix for 5.8, we're working on something to make a > recoverable error recoverable. > > > block/blk-zoned.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/block/blk-zoned.c b/block/blk-zoned.c > index 23831fa8701d..480dfff69a00 100644 > --- a/block/blk-zoned.c > +++ b/block/blk-zoned.c > @@ -497,6 +497,9 @@ int blk_revalidate_disk_zones(struct gendisk *disk, > if (WARN_ON_ONCE(!queue_is_mq(q))) > return -EIO; > > + if (!get_capacity(disk)) > + return -EIO; > + > /* > * Ensure that all memory allocations in this context are done as if > * GFP_NOIO was specified. > I reworked sd_zbc_read_zones() and sd_zbc_revalidate_zones() to allow recovering from simple temporary errors and avoid this problem. Will send the patch tomorrow or so after some more testing. But even with that patch applied, I think this patch makes the generic block code more solid. So: Reviewed-by: Damien Le Moal <damien.lemoal@xxxxxxx> -- Damien Le Moal Western Digital Research
