Re: block: zero logical block size leads to infinite loop in set_init_blocksize()

[Keith Busch <kbusch@kernel.org>]

On Wed, Sep 09, 2026 at 10:11:07PM +0300, Maks wrote:
> Hi,
> 
> > How did you manage to get a block_device created, but bypassed the check
> > and override for a zero logical block size in blk_validate_limits()? Is
> > your driver writing over the limits outside the API's update path?
> 
> Yes, it does update the queue limits directly:
> 
>     volume->queue->limits = limits;
> 
> There is no blk_validate_limits() call on this path, so this bypasses the
> normal queue limits validation.
> 
> Given that the driver is clearly bypassing the normal queue limits
> validation, would a defensive check in set_init_blocksize() still be
> considered worthwhile to avoid the infinite loop in this case?

There's just a lot more places than set_init_blocksize() that assumes
bdev_logical_block_size() returns a validated value. If you've a driver
bypassing the API's that manage this field, then there's many other
functions that also won't work correctly.