[PATCH 1/4] arm64: memblock: don't permit memblock resizing until linear mapping is up

[will.deacon@arm.com (Will Deacon)]

On Tue, Nov 06, 2018 at 12:37:29PM +0100, Ard Biesheuvel wrote:
> Bhupesh reports that having numerous memblock reservations at early
> boot may result in the following crash:
> 
>   Unable to handle kernel paging request at virtual address ffff80003ffe0000
>   ...
>   Call trace:
>    __memcpy+0x110/0x180
>    memblock_add_range+0x134/0x2e8
>    memblock_reserve+0x70/0xb8
>    memblock_alloc_base_nid+0x6c/0x88
>    __memblock_alloc_base+0x3c/0x4c
>    memblock_alloc_base+0x28/0x4c
>    memblock_alloc+0x2c/0x38
>    early_pgtable_alloc+0x20/0xb0
>    paging_init+0x28/0x7f8
> 
> This is caused by the fact that we permit memblock resizing before the
> linear mapping is up, and so the memblock_reserved() array is moved
> into memory that is not mapped yet.
> 
> So let's ensure that this crash can no longer occur, by deferring to
> call to memblock_allow_resize() to after the linear mapping has been
> created.
> 
> Reported-by: Bhupesh Sharma <bhsharma@redhat.com>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> ---
>  arch/arm64/mm/init.c | 2 --
>  arch/arm64/mm/mmu.c  | 2 ++
>  2 files changed, 2 insertions(+), 2 deletions(-)

Thanks for posting this so quickly.

Acked-by: Will Deacon <will.deacon@arm.com>

Bhupesh -- please can you give this series a spin and confirm that it fixes
the problem you were seeing?

Thanks,

Will