[PATCH] arm64: Fix map_range() not splitting mapped blocks

[Fabio Estevam]

Hi Pierre,

On Mon, Mar 18, 2024 at 4:35 PM Pierre-Clément Tosi <ptosi at google.com> wrote:
>
> The implementation of map_range() creates the requested mapping by
> walking the page tables, iterating over multiple PTEs and/or descending
> into existing table mappings as needed. When doing so, it assumes any
> pre-existing valid PTE to be a table mapping. This assumption is wrong
> if the platform code attempts to successively map two overlapping ranges
> where the latter intersects a block mapping created for the former.
>
> As a result, map_range() treats the existing block mapping as a table
> mapping and descends into it i.e. starts interpreting the
> previously-mapped range as an array of PTEs, writing to them and
> potentially even descending further (extra fun with MMIO ranges!).
>
> Instead, pass any valid non-table mapping to split_block(), which
> ensures that it actually was a block mapping (calls panic() otherwise)
> before splitting it.
>
> Fixes: 41e2787f5ec4 ("arm64: Reduce add_map() complexity")
> Signed-off-by: Pierre-Clément Tosi <ptosi at google.com>

This fixes the boot regression on colibri-imx8x.

Thanks a lot for your fix!

Tested-by: Fabio Estevam <festevam at gmail.com>