Messages in this thread | | | Date | Fri, 10 Jun 2022 13:06:22 +0800 | Subject | Re: Re: [PATCH v2 1/1] mm/memory-failure: don't allow to unpoison hw corrupted page | From | zhenwei pi <> |
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On 6/8/22 17:30, David Hildenbrand wrote: > On 08.06.22 10:43, zhenwei pi wrote: >> Currently unpoison_memory(unsigned long pfn) is designed for soft >> poison(hwpoison-inject) only. Since 17fae1294ad9d, the KPTE gets >> cleared on a x86 platform once hardware memory corrupts. >> >> Unpoisoning a hardware corrupted page puts page back buddy only, >> the kernel has a chance to access the page with *NOT PRESENT* KPTE. >> This leads BUG during accessing on the corrupted KPTE. >> >> Do not allow to unpoison hardware corrupted page in unpoison_memory() to >> avoid BUG like this: >> >> Unpoison: Software-unpoisoned page 0x61234 >> BUG: unable to handle page fault for address: ffff888061234000 >> #PF: supervisor write access in kernel mode >> #PF: error_code(0x0002) - not-present page >> PGD 2c01067 P4D 2c01067 PUD 107267063 PMD 10382b063 PTE 800fffff9edcb062 >> Oops: 0002 [#1] PREEMPT SMP NOPTI >> CPU: 4 PID: 26551 Comm: stress Kdump: loaded Tainted: G M OE 5.18.0.bm.1-amd64 #7 >> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996) ... >> RIP: 0010:clear_page_erms+0x7/0x10 >> Code: ... >> RSP: 0000:ffffc90001107bc8 EFLAGS: 00010246 >> RAX: 0000000000000000 RBX: 0000000000000901 RCX: 0000000000001000 >> RDX: ffffea0001848d00 RSI: ffffea0001848d40 RDI: ffff888061234000 >> RBP: ffffea0001848d00 R08: 0000000000000901 R09: 0000000000001276 >> R10: 0000000000000003 R11: 0000000000000000 R12: 0000000000000001 >> R13: 0000000000000000 R14: 0000000000140dca R15: 0000000000000001 >> FS: 00007fd8b2333740(0000) GS:ffff88813fd00000(0000) knlGS:0000000000000000 >> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> CR2: ffff888061234000 CR3: 00000001023d2005 CR4: 0000000000770ee0 >> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 >> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 >> PKRU: 55555554 >> Call Trace: >> <TASK> >> prep_new_page+0x151/0x170 >> get_page_from_freelist+0xca0/0xe20 >> ? sysvec_apic_timer_interrupt+0xab/0xc0 >> ? asm_sysvec_apic_timer_interrupt+0x1b/0x20 >> __alloc_pages+0x17e/0x340 >> __folio_alloc+0x17/0x40 >> vma_alloc_folio+0x84/0x280 >> __handle_mm_fault+0x8d4/0xeb0 >> handle_mm_fault+0xd5/0x2a0 >> do_user_addr_fault+0x1d0/0x680 >> ? kvm_read_and_reset_apf_flags+0x3b/0x50 >> exc_page_fault+0x78/0x170 >> asm_exc_page_fault+0x27/0x30 >> >> Fixes: 847ce401df392 ("HWPOISON: Add unpoisoning support") >> Fixes: 17fae1294ad9d ("x86/{mce,mm}: Unmap the entire page if the whole page is affected and poisoned") >> Cc: Naoya Horiguchi <naoya.horiguchi@nec.com> >> Signed-off-by: zhenwei pi <pizhenwei@bytedance.com> >> --- >> mm/memory-failure.c | 9 +++++++++ >> 1 file changed, 9 insertions(+) >> >> diff --git a/mm/memory-failure.c b/mm/memory-failure.c >> index b85661cbdc4a..da99a2b7ef35 100644 >> --- a/mm/memory-failure.c >> +++ b/mm/memory-failure.c >> @@ -2090,6 +2090,7 @@ int unpoison_memory(unsigned long pfn) >> { >> struct page *page; >> struct page *p; >> + pte_t *kpte; >> int ret = -EBUSY; >> int freeit = 0; >> static DEFINE_RATELIMIT_STATE(unpoison_rs, DEFAULT_RATELIMIT_INTERVAL, >> @@ -2103,6 +2104,14 @@ int unpoison_memory(unsigned long pfn) >> >> mutex_lock(&mf_mutex); >> >> + kpte = virt_to_kpte((unsigned long)page_to_virt(p)); >> > I'm curious whether virt_to_kpte is sane to use, especially, when having > the direct map map PMDs and not PTEs? > > virt_to_kpte() only checks for pmd_none() -- but what if we have > pmd_large()? > > Naive me would assume that calling virt_to_kpte() from generic code is > broken. Only mm/highmem.c uses it, however, 32bit most probably also > doesn't have large mappings in the page tables for the direct map. >
Hi,
I dived into this part and noticed that both pmd_off_k() and virt_to_kpte() are broken.
For example, on a x86 platform, if the CPU has feature 'pdpe1gb', the kernel prefers 1G map. (cat /proc/meminfo | grep DirectMap to show the current mapping)
static inline pmd_t *pmd_off_k(unsigned long va) { return pmd_offset(pud_offset(p4d_offset(pgd_offset_k(va), va), va), va); }
There is no pud_none() & pud_large()(of cause, we can't use pud_large() here) to test *PUD* valid or not.
So I'm going to do: - in pmd_off_k(), use pud_none() and pud_bad() to test *PUD*, if failed, BUG(). - in virt_to_kpte(), use pmd_none() & pmd_bad() to test *PMD*, if failed, BUG(). - rework KPTE test in unpoison_memory(), walk page table instead of useing virt_to_kpte().
Do you have any suggestions?
-- zhenwei pi
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