Re: [PATCH] md: add max_disks bound check in older version

[syzbot <syzbot+9e3014263a35700ab49b@syzkaller.appspotmail.com>]

> #syz test

"" does not look like a valid git branch or commit.

>
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 680b34a63cb3..f5fce41637f1 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -1693,6 +1693,12 @@ static void super_90_sync(struct mddev *mddev, struct md_rdev *rdev)
>  			desc_nr = rdev2->raid_disk;
>  		else
>  			desc_nr = next_spare++;
> +
> +		if (desc_nr >= MD_SB_DISKS) {
> +			pr_warn("md: raid_disks = %d exceeds max_disks = %d for version 0.90\n",
> +					desc_nr, MD_SB_DISKS);
> +			continue;
> +		}
>  		rdev2->desc_nr = desc_nr;
>  		d = &sb->disks[rdev2->desc_nr];
>  		nr_disks++;
> @@ -1722,7 +1728,7 @@ static void super_90_sync(struct mddev *mddev, struct md_rdev *rdev)
>  			d->state |= (1<<MD_DISK_FAILFAST);
>  	}
>  	/* now set the "removed" and "faulty" bits on any missing devices */
> -	for (i=0 ; i < mddev->raid_disks ; i++) {
> +	for (i = 0; i < mddev->raid_disks && i < MD_SB_DISKS; i++) {
>  		mdp_disk_t *d = &sb->disks[i];
>  		if (d->state == 0 && d->number == 0) {
>  			d->number = i;
> --
> 2.55.0
>