On Fri, Feb 19, 2021 at 2:18 PM Will Deacon [off-list ref] wrote:

On Tue, Feb 16, 2021 at 10:03:51AM -0500, Pavel Tatashin wrote:

quoted

Memory hotplug may fail on systems with CONFIG_RANDOMIZE_BASE because the
linear map range is not checked correctly.

The start physical address that linear map covers can be actually at the
end of the range because of randomization. Check that and if so reduce it
to 0.

This can be verified on QEMU with setting kaslr-seed to ~0ul:

memstart_offset_seed = 0xffff
START: __pa(_PAGE_OFFSET(vabits_actual)) = ffff9000c0000000
END:   __pa(PAGE_END - 1) =  1000bfffffff

Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Fixes: 58284a901b42 ("arm64/mm: Validate hotplug range before creating linear mapping")
Tested-by: Tyler Hicks <redacted>
---
 arch/arm64/mm/mmu.c | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

I tried to queue this as a fix, but unfortunately it doesn't apply.
Please can you send a v4 based on the arm64 for-next/fixes branch?

Hi Will,

The previous version, that is not built against linux-next would still
applies against current mainlein/for-next/fixes

https://lore.kernel.org/lkml/20210215192237.362706-2-pasha.tatashin@soleen.com/ (local)

I just tried it. I think it would make sense to take v2 fix, so it
could also be backported to stables.

Thank you,
Pasha