Re: [PATCH v2 1/2] dm array: validate array block headers on read

[Bryam Vargas <hexlabsecurity@proton.me>]

On Mon, Aug 03, 2026 at 09:41:36PM +0800, Ming-Hung Tsai wrote:
> One minor nit, which needn't hold up the patch: I'd drop "wanted %u"
> from the error message. The wanted value is derivable from value_size,
> so printing "%s failed: max_entries %u invalid for value_size %u"
> carries the same information.

I'd keep it. The two DMERR_LIMITs above it in array_block_check() are
"blocknr %llu != wanted %llu" and "csum %u != wanted %u", so "%u != wanted
%u" is the shape a reader of this function already expects. You're right
that the wanted value follows from value_size here and doesn't there --
what I was matching is the form, not the information content. Mikulas,
drop it when applying if you'd rather.

> Reproducer to validate the BUG_ON prevention using crafted metadata:
> create a cache device, and reduce the max_entries of the final array
> block of the mapping array. Next, expand the fast device to make the
> last array block exceeds its capacity, which triggers the BUG_ON in
> fill_ablock().

That is the path the equality test is there for -- an upper bound lets a
short max_entries through to fill_ablock() untouched. My A/B covered the
overread only, so that half was by inspection.

Thanks for the review.

Bryam