On Fri, Jan 27, 2023 at 12:43:17PM +0000, Robin Murphy wrote:

On 2023-01-26 13:33, Will Deacon wrote:

quoted

On Tue, Jan 24, 2023 at 11:11:49AM +0530, Anshuman Khandual wrote:

quoted

On 1/9/23 10:58, Anshuman Khandual wrote:

quoted

Changing pfn on a user page table mapped entry, without first going through
break-before-make (BBM) procedure is unsafe. This just updates set_pte_at()
to intercept such changes, via an updated pgattr_change_is_safe(). This new
check happens via __check_racy_pte_update(), which has now been renamed as
__check_safe_pte_update().

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Anshuman Khandual <redacted>
---
This applies on v6.2-rc3. This patch had some test time on an internal CI
system without any issues being reported.

Gentle ping, any updates on this patch ? Still any concerns ?

I don't think we really got to the bottom of Mark's concerns with
unreachable ptes on the stack, did we? I also have vague recollections
of somebody (Robin?) running into issues with the vmap code not honouring
BBM.

Doesn't ring a bell, so either it wasn't me, or it was many years ago and
about 5 levels deep into trying to fix something else :/

Bah, sorry! Catalin reckons it may have been him talking about the vmemmap.
Catalin -- any clues?

Will

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