| 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, 12 Sep 2016 10:05:36 -0500
From: Tom Lendacky <thomas.lendacky@....com>
To: Borislav Petkov <bp@...en8.de>
CC: <linux-arch@...r.kernel.org>, <linux-efi@...r.kernel.org>,
<kvm@...r.kernel.org>, <linux-doc@...r.kernel.org>,
<x86@...nel.org>, <linux-kernel@...r.kernel.org>,
<kasan-dev@...glegroups.com>, <linux-mm@...ck.org>,
<iommu@...ts.linux-foundation.org>,
Radim Krčmář <rkrcmar@...hat.com>,
Arnd Bergmann <arnd@...db.de>,
Jonathan Corbet <corbet@....net>,
Matt Fleming <matt@...eblueprint.co.uk>,
Joerg Roedel <joro@...tes.org>,
Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
Andrey Ryabinin <aryabinin@...tuozzo.com>,
Ingo Molnar <mingo@...hat.com>,
Andy Lutomirski <luto@...nel.org>,
"H. Peter Anvin" <hpa@...or.com>,
Paolo Bonzini <pbonzini@...hat.com>,
Alexander Potapenko <glider@...gle.com>,
Thomas Gleixner <tglx@...utronix.de>,
Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [RFC PATCH v2 10/20] x86: Insure that memory areas are encrypted
when possible
On 09/09/2016 10:53 AM, Borislav Petkov wrote:
> On Mon, Aug 22, 2016 at 05:37:23PM -0500, Tom Lendacky wrote:
>> Encrypt memory areas in place when possible (e.g. zero page, etc.) so
>> that special handling isn't needed afterwards.
>>
>> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
>> ---
>> arch/x86/kernel/head64.c | 93 ++++++++++++++++++++++++++++++++++++++++++++--
>> arch/x86/kernel/setup.c | 8 ++++
>> 2 files changed, 96 insertions(+), 5 deletions(-)
>
> ...
>
>> +int __init early_make_pgtable(unsigned long address)
>> +{
>> + unsigned long physaddr = address - __PAGE_OFFSET;
>> + pmdval_t pmd;
>> +
>> + pmd = (physaddr & PMD_MASK) + early_pmd_flags;
>> +
>> + return __early_make_pgtable(address, pmd);
>> +}
>> +
>> +static void __init create_unencrypted_mapping(void *address, unsigned long size)
>> +{
>> + unsigned long physaddr = (unsigned long)address - __PAGE_OFFSET;
>> + pmdval_t pmd_flags, pmd;
>> +
>> + if (!sme_me_mask)
>> + return;
>> +
>> + /* Clear the encryption mask from the early_pmd_flags */
>> + pmd_flags = early_pmd_flags & ~sme_me_mask;
>> +
>> + do {
>> + pmd = (physaddr & PMD_MASK) + pmd_flags;
>> + __early_make_pgtable((unsigned long)address, pmd);
>> +
>> + address += PMD_SIZE;
>> + physaddr += PMD_SIZE;
>> + size = (size < PMD_SIZE) ? 0 : size - PMD_SIZE;
>> + } while (size);
>> +}
>> +
>> +static void __init __clear_mapping(unsigned long address)
>
> Should be called something with "pmd" in the name as it clears a PMD,
> i.e. __clear_pmd_mapping or so.
Ok.
>
>> +{
>> + unsigned long physaddr = address - __PAGE_OFFSET;
>> + pgdval_t pgd, *pgd_p;
>> + pudval_t pud, *pud_p;
>> + pmdval_t *pmd_p;
>> +
>> + /* Invalid address or early pgt is done ? */
>> + if (physaddr >= MAXMEM ||
>> + read_cr3() != __sme_pa_nodebug(early_level4_pgt))
>> + return;
>> +
>> + pgd_p = &early_level4_pgt[pgd_index(address)].pgd;
>> + pgd = *pgd_p;
>> +
>> + if (!pgd)
>> + return;
>> +
>> + /*
>> + * The use of __START_KERNEL_map rather than __PAGE_OFFSET here matches
>> + * __early_make_pgtable where the entry was created.
>> + */
>> + pud_p = (pudval_t *)((pgd & PTE_PFN_MASK) + __START_KERNEL_map - phys_base);
>> + pud_p += pud_index(address);
>> + pud = *pud_p;
>> +
>> + if (!pud)
>> + return;
>> +
>> + pmd_p = (pmdval_t *)((pud & PTE_PFN_MASK) + __START_KERNEL_map - phys_base);
>> + pmd_p[pmd_index(address)] = 0;
>> +}
>> +
>> +static void __init clear_mapping(void *address, unsigned long size)
>> +{
>> + if (!sme_me_mask)
>> + return;
>> +
>> + do {
>> + __clear_mapping((unsigned long)address);
>> +
>> + address += PMD_SIZE;
>> + size = (size < PMD_SIZE) ? 0 : size - PMD_SIZE;
>> + } while (size);
>> +}
>> +
>> +static void __init sme_memcpy(void *dst, void *src, unsigned long size)
>> +{
>> + create_unencrypted_mapping(src, size);
>> + memcpy(dst, src, size);
>> + clear_mapping(src, size);
>> +}
>> +
>
> In any case, this whole functionality is SME-specific and should be
> somewhere in an SME-specific file. arch/x86/mm/mem_encrypt.c or so...
I can look into that. The reason I put this here is this is all the
early page fault support that is very specific to this file. I modified
an existing static function to take advantage of the mapping support.
>
>> /* Don't add a printk in there. printk relies on the PDA which is not initialized
>> yet. */
>> static void __init clear_bss(void)
>> @@ -122,12 +205,12 @@ static void __init copy_bootdata(char *real_mode_data)
>> char * command_line;
>> unsigned long cmd_line_ptr;
>>
>> - memcpy(&boot_params, real_mode_data, sizeof boot_params);
>> + sme_memcpy(&boot_params, real_mode_data, sizeof boot_params);
>
> checkpatch.pl:
>
> WARNING: sizeof boot_params should be sizeof(boot_params)
> #155: FILE: arch/x86/kernel/head64.c:208:
> + sme_memcpy(&boot_params, real_mode_data, sizeof boot_params);
I can fix that.
>
>> sanitize_boot_params(&boot_params);
>> cmd_line_ptr = get_cmd_line_ptr();
>> if (cmd_line_ptr) {
>> command_line = __va(cmd_line_ptr);
>> - memcpy(boot_command_line, command_line, COMMAND_LINE_SIZE);
>> + sme_memcpy(boot_command_line, command_line, COMMAND_LINE_SIZE);
>> }
>> }
>>
>> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
>> index 1489da8..1fdaa11 100644
>> --- a/arch/x86/kernel/setup.c
>> +++ b/arch/x86/kernel/setup.c
>> @@ -114,6 +114,7 @@
>> #include <asm/microcode.h>
>> #include <asm/mmu_context.h>
>> #include <asm/kaslr.h>
>> +#include <asm/mem_encrypt.h>
>>
>> /*
>> * max_low_pfn_mapped: highest direct mapped pfn under 4GB
>> @@ -376,6 +377,13 @@ static void __init reserve_initrd(void)
>> !ramdisk_image || !ramdisk_size)
>> return; /* No initrd provided by bootloader */
>>
>> + /*
>> + * This memory is marked encrypted by the kernel but the ramdisk
>> + * was loaded in the clear by the bootloader, so make sure that
>> + * the ramdisk image is encrypted.
>> + */
>> + sme_early_mem_enc(ramdisk_image, ramdisk_end - ramdisk_image);
>
> What happens if we go and relocate the ramdisk? I.e., the function above
> this one: relocate_initrd(). We have to encrypt it then too, I presume.
Hmmm, maybe... With the change to the early_memremap() the initrd is now
identified as BOOT_DATA in relocate_initrd() and so it will be mapped
and copied as non-encyrpted data. But since it was encrypted before the
call to relocate_initrd() it will copy encrypted bytes which will later
be accessed encrypted. That isn't clear though, so I'll rework
reserve_initrd() to perform the sme_early_mem_enc() once at the end
whether the initrd is re-located or not.
Thanks,
Tom
>
Powered by blists - more mailing lists