[Drbd-dev] [PATCH v2 1/3] md: Fix undefined behaviour in is_mddev_idle
Li Jinlin
lijinlin3 at huawei.com
Fri Dec 10 09:46:26 CET 2021
On 12/10/2021 3:17 PM, Damien Le Moal wrote:
> On 2021/12/10 15:45, Hannes Reinecke wrote:
>> On 12/10/21 6:17 AM, Li Jinlin wrote:
>>> UBSAN reports this problem:
>>>
>>> [ 5984.281385] UBSAN: Undefined behaviour in drivers/md/md.c:8175:15
>>> [ 5984.281390] signed integer overflow:
>>> [ 5984.281393] -2147483291 - 2072033152 cannot be represented in type 'int'
>>> [ 5984.281400] CPU: 25 PID: 1854 Comm: md101_resync Kdump: loaded Not tainted 4.19.90
>>> [ 5984.281404] Hardware name: Huawei TaiShan 200 (Model 5280)/BC82AMDDA
>>> [ 5984.281406] Call trace:
>>> [ 5984.281415] dump_backtrace+0x0/0x310
>>> [ 5984.281418] show_stack+0x28/0x38
>>> [ 5984.281425] dump_stack+0xec/0x15c
>>> [ 5984.281430] ubsan_epilogue+0x18/0x84
>>> [ 5984.281434] handle_overflow+0x14c/0x19c
>>> [ 5984.281439] __ubsan_handle_sub_overflow+0x34/0x44
>>> [ 5984.281445] is_mddev_idle+0x338/0x3d8
>>> [ 5984.281449] md_do_sync+0x1bb8/0x1cf8
>>> [ 5984.281452] md_thread+0x220/0x288
>>> [ 5984.281457] kthread+0x1d8/0x1e0
>>> [ 5984.281461] ret_from_fork+0x10/0x18
>>>
>>> When the stat aacum of the disk is greater than INT_MAX, its
>>> value becomes negative after casting to 'int', which may lead
>>> to overflow after subtracting a positive number. In the same
>>> way, when the value of sync_io is greater than INT_MAX,
>>> overflow may also occur. These situations will lead to
>>> undefined behavior.
>>>
>>> Otherwise, if the stat accum of the disk is close to INT_MAX
>>> when creating raid arrays, the initial value of last_events
>>> would be set close to INT_MAX when mddev initializes IO
>>> event counters. 'curr_events - rdev->last_events > 64' will
>>> always false during synchronization. If all the disks of mddev
>>> are in this case, is_mddev_idle() will always return 1, which
>>> may cause non-sync IO is very slow.
>>>
>>> To address these problems, need to use 64bit signed integer
>>> type for sync_io, last_events, and curr_events.
>>>
>>> In all the drivers that come with the kernel, the sync_io
>>> variable in struct gendisk is only used for the md driver
>>> currently. It should be more suitable in struct md_rdev, so
>>> add the sync_io variable in struct md_rdev, and use it to
>>> replace. We modify md_sync_acct() and md_sync_acct_bio()
>>> to fit for this change as well. md_sync_acct_bio() need
>>> access to the rdev, so we set bio->bi_bdev to rdev before
>>> calling it, and reset bio->bi_bdev to bdev in this function.
>>>
>> Please make that two patches, one for moving sync_io and one for
>> fixing the undefined behaviour.
ok.
>>
>>> Signed-off-by: Li Jinlin <lijinlin3 at huawei.com>
>>> ---
>>> drivers/md/md.c | 6 +++---
>>> drivers/md/md.h | 13 +++++++++----
>>> drivers/md/raid1.c | 4 ++--
>>> drivers/md/raid10.c | 24 ++++++++++++------------
>>> drivers/md/raid5.c | 4 ++--
>>> include/linux/genhd.h | 1 -
>>> 6 files changed, 28 insertions(+), 24 deletions(-)
>>>
>>> diff --git a/drivers/md/md.c b/drivers/md/md.c
>>> index 5111ed966947..f1b71a92801e 100644
>>> --- a/drivers/md/md.c
>>> +++ b/drivers/md/md.c
>>> @@ -8429,14 +8429,14 @@ static int is_mddev_idle(struct mddev *mddev, int init)
>>> {
>>> struct md_rdev *rdev;
>>> int idle;
>>> - int curr_events;
>>> + s64 curr_events;
>>>
>>> idle = 1;
>>> rcu_read_lock();
>>> rdev_for_each_rcu(rdev, mddev) {
>>> struct gendisk *disk = rdev->bdev->bd_disk;
>>> - curr_events = (int)part_stat_read_accum(disk->part0, sectors) -
>>> - atomic_read(&disk->sync_io);
>>> + curr_events = (s64)part_stat_read_accum(disk->part0, sectors) -
>>> + atomic64_read(&rdev->sync_io);
>>
>> So you are replacing a 'signed integer' (ie 32bit) calculation with a
>> 'signed 64-bit integer' calculation.
>> IE you just shifted the overflow from INT_MAX to LONG_MAX, without
>> actually fixing it, or?
Yes, for the disk with 512-byte sector sizes, the data size of INT_MAX
sectors is 1T. LONG_MAX is enough to use until the server restarts,
and overflow will not occur anymore.
>>
>>> /* sync IO will cause sync_io to increase before the disk_stats
>>> * as sync_io is counted when a request starts, and
>>> * disk_stats is counted when it completes.
>>> diff --git a/drivers/md/md.h b/drivers/md/md.h
>>> index 53ea7a6961de..584e357e0940 100644
>>> --- a/drivers/md/md.h
>>> +++ b/drivers/md/md.h
>>> @@ -50,7 +50,7 @@ struct md_rdev {
>>>
>>> sector_t sectors; /* Device size (in 512bytes sectors) */
>>> struct mddev *mddev; /* RAID array if running */
>>> - int last_events; /* IO event timestamp */
>>> + s64 last_events; /* IO event timestamp */
>>>
>>> /*
>>> * If meta_bdev is non-NULL, it means that a separate device is
>>> @@ -138,6 +138,8 @@ struct md_rdev {
>>> unsigned int size; /* Size in sectors of the PPL space */
>>> sector_t sector; /* First sector of the PPL space */
>>> } ppl;
>>> +
>>> + atomic64_t sync_io; /* counter of sync IO (unit sectors) */
>>> };
>>> enum flag_bits {
>>> Faulty, /* device is known to have a fault */
>>> @@ -549,14 +551,17 @@ static inline int mddev_trylock(struct mddev *mddev)
>>> }
>>> extern void mddev_unlock(struct mddev *mddev);
>>>
>>> -static inline void md_sync_acct(struct block_device *bdev, unsigned long nr_sectors)
>>> +static inline void md_sync_acct(struct md_rdev *rdev, unsigned long nr_sectors)
>>> {
>>> - atomic_add(nr_sectors, &bdev->bd_disk->sync_io);
>>> + atomic64_add(nr_sectors, &rdev->sync_io);
>>> }
>>>
>>> static inline void md_sync_acct_bio(struct bio *bio, unsigned long nr_sectors)
>>> {
>>> - md_sync_acct(bio->bi_bdev, nr_sectors);
>>> + struct md_rdev *rdev = (void *)bio->bi_bdev;
>>
>> That look weird. bio->bi_bdev should be a 'struct gendisk', not a MD
>> internal data structure.
>
> You mean a "struct block_device". right ? :)
>
Here is a difficult point for moving sync_io. We need a good way
to slove it or not move sync_io.
>>
>>> +
>>> + bio_set_dev(bio, rdev->bdev);
>>> + md_sync_acct(rdev, nr_sectors);
>>> }
>>>
>>> struct md_personality
>>> diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
>>> index 7dc8026cf6ee..74c42dabe57c 100644
>>> --- a/drivers/md/raid1.c
>>> +++ b/drivers/md/raid1.c
>>> @@ -2232,7 +2232,7 @@ static void sync_request_write(struct mddev *mddev, struct r1bio *r1_bio)
>>>
>>> wbio->bi_end_io = end_sync_write;
>>> atomic_inc(&r1_bio->remaining);
>>> - md_sync_acct(conf->mirrors[i].rdev->bdev, bio_sectors(wbio));
>>> + md_sync_acct(conf->mirrors[i].rdev, bio_sectors(wbio));
>>>
>>> submit_bio_noacct(wbio);
>>> }
>>> @@ -2791,7 +2791,7 @@ static sector_t raid1_sync_request(struct mddev *mddev, sector_t sector_nr,
>>> if (rdev && bio->bi_end_io) {
>>> atomic_inc(&rdev->nr_pending);
>>> bio->bi_iter.bi_sector = sector_nr + rdev->data_offset;
>>> - bio_set_dev(bio, rdev->bdev);
>>> + bio->bi_bdev = (void *)rdev;
>>> if (test_bit(FailFast, &rdev->flags))
>>> bio->bi_opf |= MD_FAILFAST;
>>> }
>>> diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
>>> index dde98f65bd04..fc1e6c0996de 100644
>>> --- a/drivers/md/raid10.c
>>> +++ b/drivers/md/raid10.c
>>> @@ -2407,7 +2407,7 @@ static void sync_request_write(struct mddev *mddev, struct r10bio *r10_bio)
>>>
>>> atomic_inc(&conf->mirrors[d].rdev->nr_pending);
>>> atomic_inc(&r10_bio->remaining);
>>> - md_sync_acct(conf->mirrors[d].rdev->bdev, bio_sectors(tbio));
>>> + md_sync_acct(conf->mirrors[d].rdev, bio_sectors(tbio));
>>>
>>> if (test_bit(FailFast, &conf->mirrors[d].rdev->flags))
>>> tbio->bi_opf |= MD_FAILFAST;
>>> @@ -2430,7 +2430,7 @@ static void sync_request_write(struct mddev *mddev, struct r10bio *r10_bio)
>>> bio_copy_data(tbio, fbio);
>>> d = r10_bio->devs[i].devnum;
>>> atomic_inc(&r10_bio->remaining);
>>> - md_sync_acct(conf->mirrors[d].replacement->bdev,
>>> + md_sync_acct(conf->mirrors[d].replacement,
>>> bio_sectors(tbio));
>>> submit_bio_noacct(tbio);
>>> }
>>> @@ -2562,12 +2562,12 @@ static void recovery_request_write(struct mddev *mddev, struct r10bio *r10_bio)
>>> wbio2 = NULL;
>>> if (wbio->bi_end_io) {
>>> atomic_inc(&conf->mirrors[d].rdev->nr_pending);
>>> - md_sync_acct(conf->mirrors[d].rdev->bdev, bio_sectors(wbio));
>>> + md_sync_acct(conf->mirrors[d].rdev, bio_sectors(wbio));
>>> submit_bio_noacct(wbio);
>>> }
>>> if (wbio2) {
>>> atomic_inc(&conf->mirrors[d].replacement->nr_pending);
>>> - md_sync_acct(conf->mirrors[d].replacement->bdev,
>>> + md_sync_acct(conf->mirrors[d].replacement,
>>> bio_sectors(wbio2));
>>> submit_bio_noacct(wbio2);
>>> }
>>> @@ -3486,7 +3486,7 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
>>> from_addr = r10_bio->devs[j].addr;
>>> bio->bi_iter.bi_sector = from_addr +
>>> rdev->data_offset;
>>> - bio_set_dev(bio, rdev->bdev);
>>> + bio->bi_bdev = (void *)rdev;
>>> atomic_inc(&rdev->nr_pending);
>>> /* and we write to 'i' (if not in_sync) */
>>>
>>> @@ -3508,7 +3508,7 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
>>> bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
>>> bio->bi_iter.bi_sector = to_addr
>>> + mrdev->data_offset;
>>> - bio_set_dev(bio, mrdev->bdev);
>>> + bio->bi_bdev = (void *)mrdev;
>>> atomic_inc(&r10_bio->remaining);
>>> } else
>>> r10_bio->devs[1].bio->bi_end_io = NULL;
>>> @@ -3529,7 +3529,7 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
>>> bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
>>> bio->bi_iter.bi_sector = to_addr +
>>> mreplace->data_offset;
>>> - bio_set_dev(bio, mreplace->bdev);
>>> + bio->bi_bdev = (void *)mreplace;
>>> atomic_inc(&r10_bio->remaining);
>>> break;
>>> }
>>> @@ -3684,7 +3684,7 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
>>> if (test_bit(FailFast, &rdev->flags))
>>> bio->bi_opf |= MD_FAILFAST;
>>> bio->bi_iter.bi_sector = sector + rdev->data_offset;
>>> - bio_set_dev(bio, rdev->bdev);
>>> + bio->bi_bdev = (void *)rdev;
>>> count++;
>>>
>>> rdev = rcu_dereference(conf->mirrors[d].replacement);
>>> @@ -3706,7 +3706,7 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
>>> if (test_bit(FailFast, &rdev->flags))
>>> bio->bi_opf |= MD_FAILFAST;
>>> bio->bi_iter.bi_sector = sector + rdev->data_offset;
>>> - bio_set_dev(bio, rdev->bdev);
>>> + bio->bi_bdev = (void *)rdev;
>>> count++;
>>> rcu_read_unlock();
>>> }
>>> @@ -4865,7 +4865,7 @@ static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr,
>>>
>>> read_bio = bio_alloc_bioset(GFP_KERNEL, RESYNC_PAGES, &mddev->bio_set);
>>>
>>> - bio_set_dev(read_bio, rdev->bdev);
>>> + read_bio->bi_bdev = (void *)rdev;
>>> read_bio->bi_iter.bi_sector = (r10_bio->devs[r10_bio->read_slot].addr
>>> + rdev->data_offset);
>>> read_bio->bi_private = r10_bio;
>>> @@ -4921,7 +4921,7 @@ static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr,
>>> if (!rdev2 || test_bit(Faulty, &rdev2->flags))
>>> continue;
>>>
>>> - bio_set_dev(b, rdev2->bdev);
>>> + b->bi_bdev = (void *)rdev2;
>>> b->bi_iter.bi_sector = r10_bio->devs[s/2].addr +
>>> rdev2->new_data_offset;
>>> b->bi_end_io = end_reshape_write;
>>> @@ -5016,7 +5016,7 @@ static void reshape_request_write(struct mddev *mddev, struct r10bio *r10_bio)
>>> }
>>> atomic_inc(&rdev->nr_pending);
>>> rcu_read_unlock();
>>> - md_sync_acct_bio(b, r10_bio->sectors);
>>> + md_sync_acct(rdev, r10_bio->sectors);
>>> atomic_inc(&r10_bio->remaining);
>>> b->bi_next = NULL;
>>> submit_bio_noacct(b);
>>> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
>>> index 9c1a5877cf9f..b932282ff50a 100644
>>> --- a/drivers/md/raid5.c
>>> +++ b/drivers/md/raid5.c
>>> @@ -1167,7 +1167,7 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
>>> if (rdev) {
>>> if (s->syncing || s->expanding || s->expanded
>>> || s->replacing)
>>> - md_sync_acct(rdev->bdev, RAID5_STRIPE_SECTORS(conf));
>>> + md_sync_acct(rdev, RAID5_STRIPE_SECTORS(conf));
>>>
>>> set_bit(STRIPE_IO_STARTED, &sh->state);
>>>
>>> @@ -1234,7 +1234,7 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
>>> if (rrdev) {
>>> if (s->syncing || s->expanding || s->expanded
>>> || s->replacing)
>>> - md_sync_acct(rrdev->bdev, RAID5_STRIPE_SECTORS(conf));
>>> + md_sync_acct(rrdev, RAID5_STRIPE_SECTORS(conf));
>>>
>>> set_bit(STRIPE_IO_STARTED, &sh->state);
>>>
>>> diff --git a/include/linux/genhd.h b/include/linux/genhd.h
>>> index 74c410263113..6b84444111e4 100644
>>> --- a/include/linux/genhd.h
>>> +++ b/include/linux/genhd.h
>>> @@ -150,7 +150,6 @@ struct gendisk {
>>> struct list_head slave_bdevs;
>>> #endif
>>> struct timer_rand_state *random;
>>> - atomic_t sync_io; /* RAID */
>>> struct disk_events *ev;
>>> #ifdef CONFIG_BLK_DEV_INTEGRITY
>>> struct kobject integrity_kobj;
>>>
>>
>> Cheers,
>>
>> Hannes
>
>
Thanks,
JinLin
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