| 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
| ||
|
Message-ID: <5f76ede6-e8be-c7a9-f957-479afa2fb828@loongson.cn>
Date: Fri, 18 Oct 2024 14:23:11 +0800
From: maobibo <maobibo@...ngson.cn>
To: Huacai Chen <chenhuacai@...nel.org>, wuruiyang@...ngson.cn
Cc: Andrey Ryabinin <ryabinin.a.a@...il.com>,
Andrew Morton <akpm@...ux-foundation.org>,
David Hildenbrand <david@...hat.com>, Barry Song <baohua@...nel.org>,
loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org,
kasan-dev@...glegroups.com, linux-mm@...ck.org
Subject: Re: [PATCH v2 1/3] LoongArch: Set initial pte entry with PAGE_GLOBAL
for kernel space
On 2024/10/18 下午12:23, Huacai Chen wrote:
> On Fri, Oct 18, 2024 at 12:16 PM maobibo <maobibo@...ngson.cn> wrote:
>>
>>
>>
>> On 2024/10/18 下午12:11, Huacai Chen wrote:
>>> On Fri, Oct 18, 2024 at 11:44 AM maobibo <maobibo@...ngson.cn> wrote:
>>>>
>>>>
>>>>
>>>> On 2024/10/18 上午11:14, Huacai Chen wrote:
>>>>> Hi, Bibo,
>>>>>
>>>>> I applied this patch but drop the part of arch/loongarch/mm/kasan_init.c:
>>>>> https://git.kernel.org/pub/scm/linux/kernel/git/chenhuacai/linux-loongson.git/commit/?h=loongarch-next&id=15832255e84494853f543b4c70ced50afc403067
>>>>>
>>>>> Because kernel_pte_init() should operate on page-table pages, not on
>>>>> data pages. You have already handle page-table page in
>>>>> mm/kasan/init.c, and if we don't drop the modification on data pages
>>>>> in arch/loongarch/mm/kasan_init.c, the kernel fail to boot if KASAN is
>>>>> enabled.
>>>>>
>>>> static inline void set_pte(pte_t *ptep, pte_t pteval)
>>>> {
>>>> WRITE_ONCE(*ptep, pteval);
>>>> -
>>>> - if (pte_val(pteval) & _PAGE_GLOBAL) {
>>>> - pte_t *buddy = ptep_buddy(ptep);
>>>> - /*
>>>> - * Make sure the buddy is global too (if it's !none,
>>>> - * it better already be global)
>>>> - */
>>>> - if (pte_none(ptep_get(buddy))) {
>>>> -#ifdef CONFIG_SMP
>>>> - /*
>>>> - * For SMP, multiple CPUs can race, so we need
>>>> - * to do this atomically.
>>>> - */
>>>> - __asm__ __volatile__(
>>>> - __AMOR "$zero, %[global], %[buddy] \n"
>>>> - : [buddy] "+ZB" (buddy->pte)
>>>> - : [global] "r" (_PAGE_GLOBAL)
>>>> - : "memory");
>>>> -
>>>> - DBAR(0b11000); /* o_wrw = 0b11000 */
>>>> -#else /* !CONFIG_SMP */
>>>> - WRITE_ONCE(*buddy, __pte(pte_val(ptep_get(buddy)) | _PAGE_GLOBAL));
>>>> -#endif /* CONFIG_SMP */
>>>> - }
>>>> - }
>>>> + DBAR(0b11000); /* o_wrw = 0b11000 */
>>>> }
>>>>
>>>> No, please hold on. This issue exists about twenty years, Do we need be
>>>> in such a hurry now?
>>>>
>>>> why is DBAR(0b11000) added in set_pte()?
>>> It exists before, not added by this patch. The reason is explained in
>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v6.12-rc3&id=f93f67d06b1023313ef1662eac490e29c025c030
>> why speculative accesses may cause spurious page fault in kernel space
>> with PTE enabled? speculative accesses exists anywhere, it does not
>> cause spurious page fault.
> Confirmed by Ruiyang Wu, and even if DBAR(0b11000) is wrong, that
> means another patch's mistake, not this one. This one just keeps the
> old behavior.
> +CC Ruiyang Wu here.
Also from Ruiyang Wu, the information is that speculative accesses may
insert stale TLB, however no page fault exception.
So adding barrier in set_pte() does not prevent speculative accesses.
And you write patch here, however do not know the actual reason?
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v6.12-rc3&id=f93f67d06b1023313ef1662eac490e29c025c030
Bibo Mao
>
> Huacai
>
>>
>> Obvious you do not it and you write wrong patch.
>>
>>>
>>> Huacai
>>>
>>>>
>>>> Regards
>>>> Bibo Mao
>>>>> Huacai
>>>>>
>>>>> On Mon, Oct 14, 2024 at 11:59 AM Bibo Mao <maobibo@...ngson.cn> wrote:
>>>>>>
>>>>>> Unlike general architectures, there are two pages in one TLB entry
>>>>>> on LoongArch system. For kernel space, it requires both two pte
>>>>>> entries with PAGE_GLOBAL bit set, else HW treats it as non-global
>>>>>> tlb, there will be potential problems if tlb entry for kernel space
>>>>>> is not global. Such as fail to flush kernel tlb with function
>>>>>> local_flush_tlb_kernel_range() which only flush tlb with global bit.
>>>>>>
>>>>>> With function kernel_pte_init() added, it can be used to init pte
>>>>>> table when it is created for kernel address space, and the default
>>>>>> initial pte value is PAGE_GLOBAL rather than zero at beginning.
>>>>>>
>>>>>> Kernel address space areas includes fixmap, percpu, vmalloc, kasan
>>>>>> and vmemmap areas set default pte entry with PAGE_GLOBAL set.
>>>>>>
>>>>>> Signed-off-by: Bibo Mao <maobibo@...ngson.cn>
>>>>>> ---
>>>>>> arch/loongarch/include/asm/pgalloc.h | 13 +++++++++++++
>>>>>> arch/loongarch/include/asm/pgtable.h | 1 +
>>>>>> arch/loongarch/mm/init.c | 4 +++-
>>>>>> arch/loongarch/mm/kasan_init.c | 4 +++-
>>>>>> arch/loongarch/mm/pgtable.c | 22 ++++++++++++++++++++++
>>>>>> include/linux/mm.h | 1 +
>>>>>> mm/kasan/init.c | 8 +++++++-
>>>>>> mm/sparse-vmemmap.c | 5 +++++
>>>>>> 8 files changed, 55 insertions(+), 3 deletions(-)
>>>>>>
>>>>>> diff --git a/arch/loongarch/include/asm/pgalloc.h b/arch/loongarch/include/asm/pgalloc.h
>>>>>> index 4e2d6b7ca2ee..b2698c03dc2c 100644
>>>>>> --- a/arch/loongarch/include/asm/pgalloc.h
>>>>>> +++ b/arch/loongarch/include/asm/pgalloc.h
>>>>>> @@ -10,8 +10,21 @@
>>>>>>
>>>>>> #define __HAVE_ARCH_PMD_ALLOC_ONE
>>>>>> #define __HAVE_ARCH_PUD_ALLOC_ONE
>>>>>> +#define __HAVE_ARCH_PTE_ALLOC_ONE_KERNEL
>>>>>> #include <asm-generic/pgalloc.h>
>>>>>>
>>>>>> +static inline pte_t *pte_alloc_one_kernel(struct mm_struct *mm)
>>>>>> +{
>>>>>> + pte_t *pte;
>>>>>> +
>>>>>> + pte = (pte_t *) __get_free_page(GFP_KERNEL);
>>>>>> + if (!pte)
>>>>>> + return NULL;
>>>>>> +
>>>>>> + kernel_pte_init(pte);
>>>>>> + return pte;
>>>>>> +}
>>>>>> +
>>>>>> static inline void pmd_populate_kernel(struct mm_struct *mm,
>>>>>> pmd_t *pmd, pte_t *pte)
>>>>>> {
>>>>>> diff --git a/arch/loongarch/include/asm/pgtable.h b/arch/loongarch/include/asm/pgtable.h
>>>>>> index 9965f52ef65b..22e3a8f96213 100644
>>>>>> --- a/arch/loongarch/include/asm/pgtable.h
>>>>>> +++ b/arch/loongarch/include/asm/pgtable.h
>>>>>> @@ -269,6 +269,7 @@ extern void set_pmd_at(struct mm_struct *mm, unsigned long addr, pmd_t *pmdp, pm
>>>>>> extern void pgd_init(void *addr);
>>>>>> extern void pud_init(void *addr);
>>>>>> extern void pmd_init(void *addr);
>>>>>> +extern void kernel_pte_init(void *addr);
>>>>>>
>>>>>> /*
>>>>>> * Encode/decode swap entries and swap PTEs. Swap PTEs are all PTEs that
>>>>>> diff --git a/arch/loongarch/mm/init.c b/arch/loongarch/mm/init.c
>>>>>> index 8a87a482c8f4..9f26e933a8a3 100644
>>>>>> --- a/arch/loongarch/mm/init.c
>>>>>> +++ b/arch/loongarch/mm/init.c
>>>>>> @@ -198,9 +198,11 @@ pte_t * __init populate_kernel_pte(unsigned long addr)
>>>>>> if (!pmd_present(pmdp_get(pmd))) {
>>>>>> pte_t *pte;
>>>>>>
>>>>>> - pte = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
>>>>>> + pte = memblock_alloc_raw(PAGE_SIZE, PAGE_SIZE);
>>>>>> if (!pte)
>>>>>> panic("%s: Failed to allocate memory\n", __func__);
>>>>>> +
>>>>>> + kernel_pte_init(pte);
>>>>>> pmd_populate_kernel(&init_mm, pmd, pte);
>>>>>> }
>>>>>>
>>>>>> diff --git a/arch/loongarch/mm/kasan_init.c b/arch/loongarch/mm/kasan_init.c
>>>>>> index 427d6b1aec09..34988573b0d5 100644
>>>>>> --- a/arch/loongarch/mm/kasan_init.c
>>>>>> +++ b/arch/loongarch/mm/kasan_init.c
>>>>>> @@ -152,6 +152,8 @@ static void __init kasan_pte_populate(pmd_t *pmdp, unsigned long addr,
>>>>>> phys_addr_t page_phys = early ?
>>>>>> __pa_symbol(kasan_early_shadow_page)
>>>>>> : kasan_alloc_zeroed_page(node);
>>>>>> + if (!early)
>>>>>> + kernel_pte_init(__va(page_phys));
>>>>>> next = addr + PAGE_SIZE;
>>>>>> set_pte(ptep, pfn_pte(__phys_to_pfn(page_phys), PAGE_KERNEL));
>>>>>> } while (ptep++, addr = next, addr != end && __pte_none(early, ptep_get(ptep)));
>>>>>> @@ -287,7 +289,7 @@ void __init kasan_init(void)
>>>>>> set_pte(&kasan_early_shadow_pte[i],
>>>>>> pfn_pte(__phys_to_pfn(__pa_symbol(kasan_early_shadow_page)), PAGE_KERNEL_RO));
>>>>>>
>>>>>> - memset(kasan_early_shadow_page, 0, PAGE_SIZE);
>>>>>> + kernel_pte_init(kasan_early_shadow_page);
>>>>>> csr_write64(__pa_symbol(swapper_pg_dir), LOONGARCH_CSR_PGDH);
>>>>>> local_flush_tlb_all();
>>>>>>
>>>>>> diff --git a/arch/loongarch/mm/pgtable.c b/arch/loongarch/mm/pgtable.c
>>>>>> index eb6a29b491a7..228ffc1db0a3 100644
>>>>>> --- a/arch/loongarch/mm/pgtable.c
>>>>>> +++ b/arch/loongarch/mm/pgtable.c
>>>>>> @@ -38,6 +38,28 @@ pgd_t *pgd_alloc(struct mm_struct *mm)
>>>>>> }
>>>>>> EXPORT_SYMBOL_GPL(pgd_alloc);
>>>>>>
>>>>>> +void kernel_pte_init(void *addr)
>>>>>> +{
>>>>>> + unsigned long *p, *end;
>>>>>> + unsigned long entry;
>>>>>> +
>>>>>> + entry = (unsigned long)_PAGE_GLOBAL;
>>>>>> + p = (unsigned long *)addr;
>>>>>> + end = p + PTRS_PER_PTE;
>>>>>> +
>>>>>> + do {
>>>>>> + p[0] = entry;
>>>>>> + p[1] = entry;
>>>>>> + p[2] = entry;
>>>>>> + p[3] = entry;
>>>>>> + p[4] = entry;
>>>>>> + p += 8;
>>>>>> + p[-3] = entry;
>>>>>> + p[-2] = entry;
>>>>>> + p[-1] = entry;
>>>>>> + } while (p != end);
>>>>>> +}
>>>>>> +
>>>>>> void pgd_init(void *addr)
>>>>>> {
>>>>>> unsigned long *p, *end;
>>>>>> diff --git a/include/linux/mm.h b/include/linux/mm.h
>>>>>> index ecf63d2b0582..6909fe059a2c 100644
>>>>>> --- a/include/linux/mm.h
>>>>>> +++ b/include/linux/mm.h
>>>>>> @@ -3818,6 +3818,7 @@ void *sparse_buffer_alloc(unsigned long size);
>>>>>> struct page * __populate_section_memmap(unsigned long pfn,
>>>>>> unsigned long nr_pages, int nid, struct vmem_altmap *altmap,
>>>>>> struct dev_pagemap *pgmap);
>>>>>> +void kernel_pte_init(void *addr);
>>>>>> void pmd_init(void *addr);
>>>>>> void pud_init(void *addr);
>>>>>> pgd_t *vmemmap_pgd_populate(unsigned long addr, int node);
>>>>>> diff --git a/mm/kasan/init.c b/mm/kasan/init.c
>>>>>> index 89895f38f722..ac607c306292 100644
>>>>>> --- a/mm/kasan/init.c
>>>>>> +++ b/mm/kasan/init.c
>>>>>> @@ -106,6 +106,10 @@ static void __ref zero_pte_populate(pmd_t *pmd, unsigned long addr,
>>>>>> }
>>>>>> }
>>>>>>
>>>>>> +void __weak __meminit kernel_pte_init(void *addr)
>>>>>> +{
>>>>>> +}
>>>>>> +
>>>>>> static int __ref zero_pmd_populate(pud_t *pud, unsigned long addr,
>>>>>> unsigned long end)
>>>>>> {
>>>>>> @@ -126,8 +130,10 @@ static int __ref zero_pmd_populate(pud_t *pud, unsigned long addr,
>>>>>>
>>>>>> if (slab_is_available())
>>>>>> p = pte_alloc_one_kernel(&init_mm);
>>>>>> - else
>>>>>> + else {
>>>>>> p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
>>>>>> + kernel_pte_init(p);
>>>>>> + }
>>>>>> if (!p)
>>>>>> return -ENOMEM;
>>>>>>
>>>>>> diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
>>>>>> index edcc7a6b0f6f..c0388b2e959d 100644
>>>>>> --- a/mm/sparse-vmemmap.c
>>>>>> +++ b/mm/sparse-vmemmap.c
>>>>>> @@ -184,6 +184,10 @@ static void * __meminit vmemmap_alloc_block_zero(unsigned long size, int node)
>>>>>> return p;
>>>>>> }
>>>>>>
>>>>>> +void __weak __meminit kernel_pte_init(void *addr)
>>>>>> +{
>>>>>> +}
>>>>>> +
>>>>>> pmd_t * __meminit vmemmap_pmd_populate(pud_t *pud, unsigned long addr, int node)
>>>>>> {
>>>>>> pmd_t *pmd = pmd_offset(pud, addr);
>>>>>> @@ -191,6 +195,7 @@ pmd_t * __meminit vmemmap_pmd_populate(pud_t *pud, unsigned long addr, int node)
>>>>>> void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node);
>>>>>> if (!p)
>>>>>> return NULL;
>>>>>> + kernel_pte_init(p);
>>>>>> pmd_populate_kernel(&init_mm, pmd, p);
>>>>>> }
>>>>>> return pmd;
>>>>>> --
>>>>>> 2.39.3
>>>>>>
>>>>
>>>>
>>
>>
Powered by blists - more mailing lists