Hi Mikulas Can we fix this by this: --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -929,10 +929,10 @@ static void super_written(struct bio *bio) bio_put(bio); - rdev_dec_pending(rdev, mddev); - if (atomic_dec_and_test(&mddev->pending_writes)) wake_up(&mddev->sb_wait); + + rdev_dec_pending(rdev, mddev); } Regards Xiao On Tue, Jan 24, 2023 at 10:06 PM Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote: > > There's a theoretical race condition in md. > > super_written calls: > if (atomic_dec_and_test(&mddev->pending_writes)) > wake_up(&mddev->sb_wait); > > If the process is rescheduled just after atomic_dec_and_test and before > wake_up, it may happen that the mddev structure is freed (because > mddev->pending_writes is zero) and on scheduling back, > wake_up(&mddev->sb_wait) would access freed memory. > > Fix this bug by using an array of preallocated wait_queues, so that the > wait queue exist even after mddev was freed. > > Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx> > > --- > drivers/md/md.c | 56 ++++++++++++++++++++++++++--------------------- > drivers/md/md.h | 10 +++++++- > drivers/md/raid10.c | 4 +-- > drivers/md/raid5-cache.c | 6 ++--- > drivers/md/raid5.c | 8 +++--- > 5 files changed, 49 insertions(+), 35 deletions(-) > > Index: linux-2.6/drivers/md/md.c > =================================================================== > --- linux-2.6.orig/drivers/md/md.c > +++ linux-2.6/drivers/md/md.c > @@ -89,6 +89,9 @@ static struct workqueue_struct *md_wq; > static struct workqueue_struct *md_misc_wq; > static struct workqueue_struct *md_rdev_misc_wq; > > +wait_queue_head_t md_sb_wait_table[MD_SB_WAIT_TABLE_SIZE]; > +EXPORT_SYMBOL(md_sb_wait_table); > + > static int remove_and_add_spares(struct mddev *mddev, > struct md_rdev *this); > static void mddev_detach(struct mddev *mddev); > @@ -415,7 +418,7 @@ check_suspended: > return; > } > for (;;) { > - prepare_to_wait(&mddev->sb_wait, &__wait, > + prepare_to_wait(md_sb_wait(mddev), &__wait, > TASK_UNINTERRUPTIBLE); > if (!is_suspended(mddev, bio)) > break; > @@ -423,19 +426,19 @@ check_suspended: > schedule(); > rcu_read_lock(); > } > - finish_wait(&mddev->sb_wait, &__wait); > + finish_wait(md_sb_wait(mddev), &__wait); > } > atomic_inc(&mddev->active_io); > rcu_read_unlock(); > > if (!mddev->pers->make_request(mddev, bio)) { > atomic_dec(&mddev->active_io); > - wake_up(&mddev->sb_wait); > + wake_up_all(md_sb_wait(mddev)); > goto check_suspended; > } > > if (atomic_dec_and_test(&mddev->active_io) && mddev->suspended) > - wake_up(&mddev->sb_wait); > + wake_up_all(md_sb_wait(mddev)); > } > EXPORT_SYMBOL(md_handle_request); > > @@ -484,13 +487,13 @@ void mddev_suspend(struct mddev *mddev) > if (mddev->suspended++) > return; > synchronize_rcu(); > - wake_up(&mddev->sb_wait); > + wake_up_all(md_sb_wait(mddev)); > set_bit(MD_ALLOW_SB_UPDATE, &mddev->flags); > smp_mb__after_atomic(); > - wait_event(mddev->sb_wait, atomic_read(&mddev->active_io) == 0); > + wait_event(*md_sb_wait(mddev), atomic_read(&mddev->active_io) == 0); > mddev->pers->quiesce(mddev, 1); > clear_bit_unlock(MD_ALLOW_SB_UPDATE, &mddev->flags); > - wait_event(mddev->sb_wait, !test_bit(MD_UPDATING_SB, &mddev->flags)); > + wait_event(*md_sb_wait(mddev), !test_bit(MD_UPDATING_SB, &mddev->flags)); > > del_timer_sync(&mddev->safemode_timer); > /* restrict memory reclaim I/O during raid array is suspend */ > @@ -505,7 +508,7 @@ void mddev_resume(struct mddev *mddev) > lockdep_assert_held(&mddev->reconfig_mutex); > if (--mddev->suspended) > return; > - wake_up(&mddev->sb_wait); > + wake_up_all(md_sb_wait(mddev)); > mddev->pers->quiesce(mddev, 0); > > set_bit(MD_RECOVERY_NEEDED, &mddev->recovery); > @@ -585,7 +588,7 @@ static void md_submit_flush_data(struct > mddev->prev_flush_start = mddev->start_flush; > mddev->flush_bio = NULL; > spin_unlock_irq(&mddev->lock); > - wake_up(&mddev->sb_wait); > + wake_up_all(md_sb_wait(mddev)); > > if (bio->bi_iter.bi_size == 0) { > /* an empty barrier - all done */ > @@ -609,7 +612,7 @@ bool md_flush_request(struct mddev *mdde > /* flush requests wait until ongoing flush completes, > * hence coalescing all the pending requests. > */ > - wait_event_lock_irq(mddev->sb_wait, > + wait_event_lock_irq(*md_sb_wait(mddev), > !mddev->flush_bio || > ktime_before(req_start, mddev->prev_flush_start), > mddev->lock); > @@ -686,7 +689,6 @@ void mddev_init(struct mddev *mddev) > atomic_set(&mddev->active_io, 0); > spin_lock_init(&mddev->lock); > atomic_set(&mddev->flush_pending, 0); > - init_waitqueue_head(&mddev->sb_wait); > init_waitqueue_head(&mddev->recovery_wait); > mddev->reshape_position = MaxSector; > mddev->reshape_backwards = 0; > @@ -828,7 +830,7 @@ void mddev_unlock(struct mddev *mddev) > */ > spin_lock(&pers_lock); > md_wakeup_thread(mddev->thread); > - wake_up(&mddev->sb_wait); > + wake_up_all(md_sb_wait(mddev)); > spin_unlock(&pers_lock); > } > EXPORT_SYMBOL_GPL(mddev_unlock); > @@ -933,7 +935,7 @@ static void super_written(struct bio *bi > rdev_dec_pending(rdev, mddev); > > if (atomic_dec_and_test(&mddev->pending_writes)) > - wake_up(&mddev->sb_wait); > + wake_up_all(md_sb_wait(mddev)); > } > > void md_super_write(struct mddev *mddev, struct md_rdev *rdev, > @@ -977,7 +979,7 @@ void md_super_write(struct mddev *mddev, > int md_super_wait(struct mddev *mddev) > { > /* wait for all superblock writes that were scheduled to complete */ > - wait_event(mddev->sb_wait, atomic_read(&mddev->pending_writes)==0); > + wait_event(*md_sb_wait(mddev), atomic_read(&mddev->pending_writes)==0); > if (test_and_clear_bit(MD_SB_NEED_REWRITE, &mddev->sb_flags)) > return -EAGAIN; > return 0; > @@ -2681,7 +2683,7 @@ repeat: > wake_up(&rdev->blocked_wait); > } > } > - wake_up(&mddev->sb_wait); > + wake_up_all(md_sb_wait(mddev)); > return; > } > > @@ -2791,7 +2793,7 @@ rewrite: > BIT(MD_SB_CHANGE_DEVS) | BIT(MD_SB_CHANGE_CLEAN))) > /* have to write it out again */ > goto repeat; > - wake_up(&mddev->sb_wait); > + wake_up_all(md_sb_wait(mddev)); > if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery)) > sysfs_notify_dirent_safe(mddev->sysfs_completed); > > @@ -4383,7 +4385,7 @@ array_state_store(struct mddev *mddev, c > restart_array(mddev); > clear_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags); > md_wakeup_thread(mddev->thread); > - wake_up(&mddev->sb_wait); > + wake_up_all(md_sb_wait(mddev)); > } else /* st == clean */ { > restart_array(mddev); > if (!set_in_sync(mddev)) > @@ -4456,7 +4458,7 @@ array_state_store(struct mddev *mddev, c > if (err) > break; > clear_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags); > - wake_up(&mddev->sb_wait); > + wake_up_all(md_sb_wait(mddev)); > err = 0; > } else { > mddev->ro = MD_RDWR; > @@ -6283,7 +6285,7 @@ static int md_set_readonly(struct mddev > mddev_unlock(mddev); > wait_event(resync_wait, !test_bit(MD_RECOVERY_RUNNING, > &mddev->recovery)); > - wait_event(mddev->sb_wait, > + wait_event(*md_sb_wait(mddev), > !test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags)); > mddev_lock_nointr(mddev); > > @@ -7564,7 +7566,7 @@ static int md_ioctl(struct block_device > > if (cmd == HOT_REMOVE_DISK) > /* need to ensure recovery thread has run */ > - wait_event_interruptible_timeout(mddev->sb_wait, > + wait_event_interruptible_timeout(*md_sb_wait(mddev), > !test_bit(MD_RECOVERY_NEEDED, > &mddev->recovery), > msecs_to_jiffies(5000)); > @@ -7669,7 +7671,7 @@ static int md_ioctl(struct block_device > */ > if (test_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags)) { > mddev_unlock(mddev); > - wait_event(mddev->sb_wait, > + wait_event(*md_sb_wait(mddev), > !test_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags) && > !test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags)); > mddev_lock_nointr(mddev); > @@ -8529,7 +8531,7 @@ bool md_write_start(struct mddev *mddev, > sysfs_notify_dirent_safe(mddev->sysfs_state); > if (!mddev->has_superblocks) > return true; > - wait_event(mddev->sb_wait, > + wait_event(*md_sb_wait(mddev), > !test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags) || > mddev->suspended); > if (test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags)) { > @@ -8674,7 +8676,7 @@ void md_allow_write(struct mddev *mddev) > md_update_sb(mddev, 0); > sysfs_notify_dirent_safe(mddev->sysfs_state); > /* wait for the dirty state to be recorded in the metadata */ > - wait_event(mddev->sb_wait, > + wait_event(*md_sb_wait(mddev), > !test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags)); > } else > spin_unlock(&mddev->lock); > @@ -9256,7 +9258,7 @@ void md_check_recovery(struct mddev *mdd > if (test_bit(MD_ALLOW_SB_UPDATE, &mddev->flags)) > md_update_sb(mddev, 0); > clear_bit_unlock(MD_UPDATING_SB, &mddev->flags); > - wake_up(&mddev->sb_wait); > + wake_up_all(md_sb_wait(mddev)); > } > > if (mddev->suspended) > @@ -9420,7 +9422,7 @@ void md_check_recovery(struct mddev *mdd > sysfs_notify_dirent_safe(mddev->sysfs_action); > } > unlock: > - wake_up(&mddev->sb_wait); > + wake_up_all(md_sb_wait(mddev)); > mddev_unlock(mddev); > } > } > @@ -9608,6 +9610,10 @@ static void md_geninit(void) > static int __init md_init(void) > { > int ret = -ENOMEM; > + int i; > + > + for (i = 0; i < MD_SB_WAIT_TABLE_SIZE; i++) > + init_waitqueue_head(md_sb_wait_table + i); > > md_wq = alloc_workqueue("md", WQ_MEM_RECLAIM, 0); > if (!md_wq) > Index: linux-2.6/drivers/md/md.h > =================================================================== > --- linux-2.6.orig/drivers/md/md.h > +++ linux-2.6/drivers/md/md.h > @@ -466,7 +466,6 @@ struct mddev { > * setting MD_RECOVERY_RUNNING (which interacts with resync_{min,max}) > */ > spinlock_t lock; > - wait_queue_head_t sb_wait; /* for waiting on superblock updates */ > atomic_t pending_writes; /* number of active superblock writes */ > > unsigned int safemode; /* if set, update "clean" superblock > @@ -584,6 +583,15 @@ static inline void md_sync_acct_bio(stru > md_sync_acct(bio->bi_bdev, nr_sectors); > } > > +#define MD_SB_WAIT_TABLE_BITS 8 > +#define MD_SB_WAIT_TABLE_SIZE (1U << MD_SB_WAIT_TABLE_BITS) > +extern wait_queue_head_t md_sb_wait_table[MD_SB_WAIT_TABLE_SIZE]; > + > +static inline wait_queue_head_t *md_sb_wait(struct mddev *md) > +{ > + return md_sb_wait_table + hash_long((unsigned long)md, MD_SB_WAIT_TABLE_BITS); > +} > + > struct md_personality > { > char *name; > Index: linux-2.6/drivers/md/raid10.c > =================================================================== > --- linux-2.6.orig/drivers/md/raid10.c > +++ linux-2.6/drivers/md/raid10.c > @@ -1446,7 +1446,7 @@ static void raid10_write_request(struct > return; > } > raid10_log(conf->mddev, "wait reshape metadata"); > - wait_event(mddev->sb_wait, > + wait_event(*md_sb_wait(mddev), > !test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags)); > > conf->reshape_safe = mddev->reshape_position; > @@ -4876,7 +4876,7 @@ static sector_t reshape_request(struct m > conf->reshape_checkpoint = jiffies; > set_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags); > md_wakeup_thread(mddev->thread); > - wait_event(mddev->sb_wait, mddev->sb_flags == 0 || > + wait_event(*md_sb_wait(mddev), mddev->sb_flags == 0 || > test_bit(MD_RECOVERY_INTR, &mddev->recovery)); > if (test_bit(MD_RECOVERY_INTR, &mddev->recovery)) { > allow_barrier(conf); > Index: linux-2.6/drivers/md/raid5-cache.c > =================================================================== > --- linux-2.6.orig/drivers/md/raid5-cache.c > +++ linux-2.6/drivers/md/raid5-cache.c > @@ -691,7 +691,7 @@ static void r5c_disable_writeback_async( > mdname(mddev)); > > /* wait superblock change before suspend */ > - wait_event(mddev->sb_wait, > + wait_event(*md_sb_wait(mddev), > conf->log == NULL || > (!test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags) && > (locked = mddev_trylock(mddev)))); > @@ -1581,7 +1581,7 @@ void r5l_quiesce(struct r5l_log *log, in > if (quiesce) { > /* make sure r5l_write_super_and_discard_space exits */ > mddev = log->rdev->mddev; > - wake_up(&mddev->sb_wait); > + wake_up_all(md_sb_wait(mddev)); > kthread_park(log->reclaim_thread->tsk); > r5l_wake_reclaim(log, MaxSector); > r5l_do_reclaim(log); > @@ -3165,7 +3165,7 @@ void r5l_exit_log(struct r5conf *conf) > struct r5l_log *log = conf->log; > > /* Ensure disable_writeback_work wakes up and exits */ > - wake_up(&conf->mddev->sb_wait); > + wake_up_all(md_sb_wait(conf->mddev)); > flush_work(&log->disable_writeback_work); > md_unregister_thread(&log->reclaim_thread); > > Index: linux-2.6/drivers/md/raid5.c > =================================================================== > --- linux-2.6.orig/drivers/md/raid5.c > +++ linux-2.6/drivers/md/raid5.c > @@ -6346,7 +6346,7 @@ static sector_t reshape_request(struct m > conf->reshape_checkpoint = jiffies; > set_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags); > md_wakeup_thread(mddev->thread); > - wait_event(mddev->sb_wait, mddev->sb_flags == 0 || > + wait_event(*md_sb_wait(mddev), mddev->sb_flags == 0 || > test_bit(MD_RECOVERY_INTR, &mddev->recovery)); > if (test_bit(MD_RECOVERY_INTR, &mddev->recovery)) > return 0; > @@ -6454,7 +6454,7 @@ finish: > conf->reshape_checkpoint = jiffies; > set_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags); > md_wakeup_thread(mddev->thread); > - wait_event(mddev->sb_wait, > + wait_event(*md_sb_wait(mddev), > !test_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags) > || test_bit(MD_RECOVERY_INTR, &mddev->recovery)); > if (test_bit(MD_RECOVERY_INTR, &mddev->recovery)) > @@ -6703,7 +6703,7 @@ static void raid5_do_work(struct work_st > if (!batch_size && !released) > break; > handled += batch_size; > - wait_event_lock_irq(mddev->sb_wait, > + wait_event_lock_irq(*md_sb_wait(mddev), > !test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags), > conf->device_lock); > } > @@ -6792,7 +6792,7 @@ static void raid5d(struct md_thread *thr > continue; > } > > - wait_event_lock_irq(mddev->sb_wait, > + wait_event_lock_irq(*md_sb_wait(mddev), > !test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags), > conf->device_lock); > } > -- > dm-devel mailing list > dm-devel@xxxxxxxxxx > https://listman.redhat.com/mailman/listinfo/dm-devel > -- dm-devel mailing list dm-devel@xxxxxxxxxx https://listman.redhat.com/mailman/listinfo/dm-devel