Re: [PATCH] md/raid0: fix NULL pointer dereference in create_strip_zones() for dm-raid

[Xiao Ni]

On Sun, Nov 16, 2025 at 10:18 AM Yu Kuai <yukuai@xxxxxxxxx> wrote:
>
> Commit 2107457e31fa ("md/raid0: Move queue limit setup before r0conf
> initialization") dereference mddev->gendisk unconditionally, which is
> NULL for dm-raid.
>
> Fix this problem by reverting to old codes for dm-raid.
>
> Fixes: 2107457e31fa ("md/raid0: Move queue limit setup before r0conf initialization")
> Reported-and-tested-by: Changhui Zhong <czhong@xxxxxxxxxx>
> Closes: https://lore.kernel.org/all/CAGVVp+VqVnvGeneUoTbYvBv2cw6GwQRrR3B-iQ-_9rVfyumoKA@xxxxxxxxxxxxxx/
> Signed-off-by: Yu Kuai <yukuai@xxxxxxxxx>
> ---
>  drivers/md/raid0.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
> index 47aee1b1d4d1..985c377356eb 100644
> --- a/drivers/md/raid0.c
> +++ b/drivers/md/raid0.c
> @@ -68,7 +68,10 @@ static int create_strip_zones(struct mddev *mddev, struct r0conf **private_conf)
>         struct strip_zone *zone;
>         int cnt;
>         struct r0conf *conf = kzalloc(sizeof(*conf), GFP_KERNEL);
> -       unsigned int blksize = queue_logical_block_size(mddev->gendisk->queue);
> +       unsigned int blksize = 512;
> +
> +       if (!mddev_is_dm(mddev))
> +               blksize = queue_logical_block_size(mddev->gendisk->queue);
>
>         *private_conf = ERR_PTR(-ENOMEM);
>         if (!conf)
> @@ -84,6 +87,10 @@ static int create_strip_zones(struct mddev *mddev, struct r0conf **private_conf)
>                 sector_div(sectors, mddev->chunk_sectors);
>                 rdev1->sectors = sectors * mddev->chunk_sectors;
>
> +               if (mddev_is_dm(mddev))
> +                       blksize = max(blksize, queue_logical_block_size(
> +                                     rdev1->bdev->bd_disk->queue));
> +
>                 rdev_for_each(rdev2, mddev) {
>                         pr_debug("md/raid0:%s:   comparing %pg(%llu)"
>                                  " with %pg(%llu)\n",
> --
> 2.51.0
>

Hi all, the patch looks good to me.

Reviewed-by: Xiao Ni <xni@xxxxxxxxxx>