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md: suspend array while updating raid_disks via sysfs

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In raid1_reshape(), freeze_array() is called before modifying the r1bio
memory pool (conf->r1bio_pool) and conf->raid_disks, and
unfreeze_array() is called after the update is completed.

However, freeze_array() only waits until nr_sync_pending and
(nr_pending - nr_queued) of all buckets reaches zero. When an I/O error
occurs, nr_queued is increased and the corresponding r1bio is queued to
either retry_list or bio_end_io_list. As a result, freeze_array() may
unblock before these r1bios are released.

This can lead to a situation where conf->raid_disks and the mempool have
already been updated while queued r1bios, allocated with the old
raid_disks value, are later released. Consequently, free_r1bio() may
access memory out of bounds in put_all_bios() and release r1bios of the
wrong size to the new mempool, potentially causing issues with the
mempool as well.

Since only normal I/O might increase nr_queued while an I/O error occurs,
suspending the array avoids this issue.

Note: Updating raid_disks via ioctl SET_ARRAY_INFO already suspends
the array. Therefore, we suspend the array when updating raid_disks
via sysfs to avoid this issue too.

Signed-off-by: FengWei Shih <dannyshih@synology.com>
Link: https://lore.kernel.org/linux-raid/20251226101816.4506-1-dannyshih@synology.com
Signed-off-by: Yu Kuai <yukuai@fnnas.com>
This commit is contained in:
FengWei Shih 2025-12-26 18:18:16 +08:00 committed by Yu Kuai
parent 7ad6ef91d8
commit 2cc583653b
1 changed files with 2 additions and 2 deletions
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4
drivers/md/md.c
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@ -4404,7 +4404,7 @@ raid_disks_store(struct mddev *mddev, const char *buf, size_t len)
if (err < 0)
return err;
err = mddev_lock(mddev);
err = mddev_suspend_and_lock(mddev);
if (err)
return err;
if (mddev->pers)
@ -4429,7 +4429,7 @@ raid_disks_store(struct mddev *mddev, const char *buf, size_t len)
} else
mddev->raid_disks = n;
out_unlock:
mddev_unlock(mddev);
mddev_unlock_and_resume(mddev);
return err ? err : len;
}
static struct md_sysfs_entry md_raid_disks =