linux-kernel - Re: [PATCH v2] md: suspend array while updating raid

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <CALTww29RPghH2+x9HwtDjCAXZfgK8gBkisXNKy0k8g9d5hiV_Q@mail.gmail.com>
Date: Mon, 29 Dec 2025 17:19:52 +0800
From: Xiao Ni <xni@...hat.com>
To: dannyshih <dannyshih@...ology.com>
Cc: song@...nel.org, yukuai@...as.com, linux-raid@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] md: suspend array while updating raid_disks via sysfs

Hi FengWei and Kuai

On Fri, Dec 26, 2025 at 6:27 PM dannyshih <dannyshih@...ology.com> wrote:
>
> From: FengWei Shih <dannyshih@...ology.com>
>
> 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.

Could you explain more about this? Why can't freeze_array block when
io error occurs? If io error occurs, the nr_pending number should be
equal with nr_queued, right?

Best Regards
Xiao
>
> 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@...ology.com>
> ---
> v2:
>   * Suspend array unconditionally when updating raid_disks
>   * Refine commit message to describe the issue more concretely
> ---
>  drivers/md/md.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index e5922a682953..6bcbe1c7483c 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -4407,7 +4407,7 @@ 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)
> @@ -4432,7 +4432,7 @@ 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 =
> --
> 2.17.1
>
>
> Disclaimer: The contents of this e-mail message and any attachments are confidential and are intended solely for addressee. The information may also be legally privileged. This transmission is sent in trust, for the sole purpose of delivery to the intended recipient. If you have received this transmission in error, any use, reproduction or dissemination of this transmission is strictly prohibited. If you are not the intended recipient, please immediately notify the sender by reply e-mail or phone and delete this message and its attachments, if any.
>