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Date: Fri, 10 Dec 2021 07:45:52 +0100
From: Hannes Reinecke <hare@...e.de>
To: Li Jinlin <lijinlin3@...wei.com>, song@...nel.org,
philipp.reisner@...bit.com, lars.ellenberg@...bit.com,
axboe@...nel.dk, jack@...e.cz, ming.lei@...hat.com, tj@...nel.org,
mcgrof@...nel.org, mcroce@...rosoft.com
Cc: linux-raid@...r.kernel.org, linux-block@...r.kernel.org,
linux-kernel@...r.kernel.org, drbd-dev@...ts.linbit.com,
linfeilong@...wei.com
Subject: Re: [PATCH v2 1/3] md: Fix undefined behaviour in is_mddev_idle
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.
> Signed-off-by: Li Jinlin <lijinlin3@...wei.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?
> /* 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.
> +
> + 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
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@...e.de +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer
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