Messages in this thread | | | Date | Fri, 18 Nov 2022 14:13:18 +0000 | From | Will Deacon <> | Subject | Re: [PATCH] arm64/mm: Intercept pfn changes in set_pte_at() |
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On Wed, Nov 16, 2022 at 08:40:01AM +0530, Anshuman Khandual wrote: > 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 <anshuman.khandual@arm.com> > --- > This applies on v6.1-rc4 > > arch/arm64/include/asm/pgtable.h | 8 ++++++-- > arch/arm64/mm/mmu.c | 8 +++++++- > 2 files changed, 13 insertions(+), 3 deletions(-)
I remember Mark saying that BBM is sometimes violated by the core code in cases where the pte isn't actually part of a live pgtable (e.g. if it's on the stack or part of a newly allocated table). Won't that cause false positives here?
Will
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