lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Mon, 4 Jan 2021 15:36:33 +0000 From: Jonathan Cameron <Jonathan.Cameron@...wei.com> To: Anshuman Khandual <anshuman.khandual@....com> CC: <linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>, Mark Rutland <mark.rutland@....com>, <catalin.marinas@....com>, "David Hildenbrand" <david@...hat.com>, Robin Murphy <robin.murphy@....com>, Jérôme Glisse <jglisse@...hat.com>, James Morse <james.morse@....com>, Dan Williams <dan.j.williams@...el.com>, <will@...nel.org>, <ardb@...nel.org> Subject: Re: [RFC 1/2] arm64/mm: Fix pfn_valid() for ZONE_DEVICE based memory On Tue, 22 Dec 2020 12:42:23 +0530 Anshuman Khandual <anshuman.khandual@....com> wrote: > pfn_valid() validates a pfn but basically it checks for a valid struct page > backing for that pfn. It should always return positive for memory ranges > backed with struct page mapping. But currently pfn_valid() fails for all > ZONE_DEVICE based memory types even though they have struct page mapping. > > pfn_valid() asserts that there is a memblock entry for a given pfn without > MEMBLOCK_NOMAP flag being set. The problem with ZONE_DEVICE based memory is > that they do not have memblock entries. Hence memblock_is_map_memory() will > invariably fail via memblock_search() for a ZONE_DEVICE based address. This > eventually fails pfn_valid() which is wrong. memblock_is_map_memory() needs > to be skipped for such memory ranges. As ZONE_DEVICE memory gets hotplugged > into the system via memremap_pages() called from a driver, their respective > memory sections will not have SECTION_IS_EARLY set. > > Normal hotplug memory will never have MEMBLOCK_NOMAP set in their memblock > regions. Because the flag MEMBLOCK_NOMAP was specifically designed and set > for firmware reserved memory regions. memblock_is_map_memory() can just be > skipped as its always going to be positive and that will be an optimization > for the normal hotplug memory. Like ZONE_DEVIE based memory, all hotplugged typo: ZONE_DEVIE > normal memory too will not have SECTION_IS_EARLY set for their sections. > > Skipping memblock_is_map_memory() for all non early memory sections would > fix pfn_valid() problem for ZONE_DEVICE based memory and also improve its > performance for normal hotplug memory as well. > > Cc: Catalin Marinas <catalin.marinas@....com> > Cc: Will Deacon <will@...nel.org> > Cc: Ard Biesheuvel <ardb@...nel.org> > Cc: Robin Murphy <robin.murphy@....com> > Cc: linux-arm-kernel@...ts.infradead.org > Cc: linux-kernel@...r.kernel.org > Fixes: 73b20c84d42d ("arm64: mm: implement pte_devmap support") > Signed-off-by: Anshuman Khandual <anshuman.khandual@....com> > --- > arch/arm64/mm/init.c | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c > index 75addb36354a..ee23bda00c28 100644 > --- a/arch/arm64/mm/init.c > +++ b/arch/arm64/mm/init.c > @@ -225,6 +225,18 @@ int pfn_valid(unsigned long pfn) > > if (!valid_section(__pfn_to_section(pfn))) > return 0; > + > + /* > + * ZONE_DEVICE memory does not have the memblock entries. > + * memblock_is_map_memory() check for ZONE_DEVICE based > + * addresses will always fail. Even the normal hotplugged > + * memory will never have MEMBLOCK_NOMAP flag set in their > + * memblock entries. Skip memblock search for all non early > + * memory sections covering all of hotplug memory including > + * both normal and ZONE_DEVIE based. Here as well + the cover letter title. > + */ > + if (!early_section(__pfn_to_section(pfn))) > + return 1; > #endif > return memblock_is_map_memory(addr); > }
Powered by blists - more mailing lists