From: Ard Biesheuvel <ardb@kernel.org>
To: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
James Morris <jmorris@namei.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Logan Gunthorpe <logang@deltatee.com>,
Tyler Hicks <tyhicks@linux.microsoft.com>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Andrew Morton <akpm@linux-foundation.org>,
Will Deacon <will@kernel.org>, Mike Rapoport <rppt@kernel.org>
Subject: Re: [PATCH v2 1/1] arm64: mm: correct the inside linear map boundaries during hotplug check
Date: Mon, 15 Feb 2021 20:27:14 +0100 [thread overview]
Message-ID: <CAMj1kXGxyV0=s6jVZ674O_2amkYSnwSnubnozbzD6g6GOMJE-A@mail.gmail.com> (raw)
In-Reply-To: <20210215192237.362706-2-pasha.tatashin@soleen.com>
On Mon, 15 Feb 2021 at 20:22, Pavel Tatashin <pasha.tatashin@soleen.com> wrote:
>
> 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 <tyhicks@linux.microsoft.com>
> ---
> arch/arm64/mm/mmu.c | 20 ++++++++++++++++++--
> 1 file changed, 18 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index ae0c3d023824..cc16443ea67f 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -1444,14 +1444,30 @@ static void __remove_pgd_mapping(pgd_t *pgdir, unsigned long start, u64 size)
>
> static bool inside_linear_region(u64 start, u64 size)
> {
> + u64 start_linear_pa = __pa(_PAGE_OFFSET(vabits_actual));
> + u64 end_linear_pa = __pa(PAGE_END - 1);
> +
> + if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
> + /*
> + * Check for a wrap, it is possible because of randomized linear
> + * mapping the start physical address is actually bigger than
> + * the end physical address. In this case set start to zero
> + * because [0, end_linear_pa] range must still be able to cover
> + * all addressable physical addresses.
> + */
> + if (start_linear_pa > end_linear_pa)
> + start_linear_pa = 0;
> + }
> +
> + WARN_ON(start_linear_pa > end_linear_pa);
> +
> /*
> * Linear mapping region is the range [PAGE_OFFSET..(PAGE_END - 1)]
> * accommodating both its ends but excluding PAGE_END. Max physical
> * range which can be mapped inside this linear mapping range, must
> * also be derived from its end points.
> */
> - return start >= __pa(_PAGE_OFFSET(vabits_actual)) &&
> - (start + size - 1) <= __pa(PAGE_END - 1);
Can't we simply use signed arithmetic here? This expression works fine
if the quantities are all interpreted as s64 instead of u64
> + return start >= start_linear_pa && (start + size - 1) <= end_linear_pa;
> }
>
> int arch_add_memory(int nid, u64 start, u64 size,
> --
> 2.25.1
>
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next prev parent reply other threads:[~2021-02-15 19:28 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-15 19:22 [PATCH v2 0/1] correct the inside linear map boundaries during hotplug check Pavel Tatashin
2021-02-15 19:22 ` [PATCH v2 1/1] arm64: mm: " Pavel Tatashin
2021-02-15 19:27 ` Ard Biesheuvel [this message]
2021-02-15 19:30 ` Pavel Tatashin
2021-02-15 19:34 ` Ard Biesheuvel
2021-02-15 19:51 ` Pavel Tatashin
2021-02-15 22:28 ` Pavel Tatashin
2021-02-16 3:12 ` Anshuman Khandual
2021-02-16 7:36 ` Ard Biesheuvel
2021-02-16 14:34 ` Pavel Tatashin
2021-02-16 2:55 ` Anshuman Khandual
2021-02-16 14:48 ` Pavel Tatashin
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