On 2020/07/31 16:43, Johannes Thumshirn wrote: > On 30/07/2020 14:33, Damien Le Moal wrote: >> 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> >> >> > > Jens any chance we can still get this into 5.8? By the way, this needs a "fixes" tag too. And probably cc stable for 5.7. Looking at 5.4 LTS, the bug is not present since there is a test on !nr_zones and the entire revalidation is different anyway (callback was introduced in 5.5 if I remember correctly). -- Damien Le Moal Western Digital Research
