On 6/10/22 20:12, David Hildenbrand wrote:
On 10.06.22 13:46, 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@xxxxxxx> Cc: David Hildenbrand <david@xxxxxxxxxx> Signed-off-by: zhenwei pi <pizhenwei@xxxxxxxxxxxxx> --- mm/memory-failure.c | 59 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 59 insertions(+) diff --git a/mm/memory-failure.c b/mm/memory-failure.c index b85661cbdc4a..3124f428302c 100644 --- a/mm/memory-failure.c +++ b/mm/memory-failure.c @@ -2068,6 +2068,58 @@ static int __init memory_failure_init(void) } core_initcall(memory_failure_init);+/*+ * Unpoisoning a hardware corrupted page with *NOT PRESENT* KPTE leads panic. + * Test a page is valid in the kernel mapping. + */ +static bool kmap_valid(struct page *page) +{ + unsigned long addr = (unsigned long)page_to_virt(page); + pgd_t *pgd; + p4d_t *p4d; + pud_t *pud; + pmd_t *pmd; + pte_t *pte; + + pgd = pgd_offset_k(addr); + if (pgd_none(*pgd)) + return false; + if (pgd_leaf(*pgd)) + return true; + if (pgd_bad(*pgd)) + return false; + + p4d = p4d_offset(pgd, addr); + if (p4d_none(*p4d)) + return false; + if (p4d_leaf(*p4d)) + return true; + if (p4d_bad(*p4d)) + return false; + + pud = pud_offset(p4d, addr); + if (pud_none(*pud)) + return false; + if (pud_leaf(*pud)) + return true; + if (pud_bad(*pud)) + return false; + + pmd = pmd_offset(pud, addr); + if (pmd_none(*pmd)) + return false; + if (pmd_leaf(*pmd)) + return true; + if (pmd_bad(*pmd)) + return false; + + pte = pte_offset_map(pmd, addr); + if (pte_none(*pte) || !pte_present(*pte)) + return false; + + return true; +} + #define unpoison_pr_info(fmt, pfn, rs) \ ({ \ if (__ratelimit(rs)) \ @@ -2109,6 +2161,13 @@ int unpoison_memory(unsigned long pfn) goto unlock_mutex; }+ if (!kmap_valid(page)) {+ unpoison_pr_info("Unpoison: Page was hardware poisoned %#lx\n", + pfn, &unpoison_rs); + ret = -EOPNOTSUPP; + goto unlock_mutex; + } + if (page_count(page) > 1) { unpoison_pr_info("Unpoison: Someone grabs the hwpoison page %#lx\n", pfn, &unpoison_rs);I really prefer just disabling the unpoisioning mechanism in case there is a real hw injected error.
Hi, Naoya & Andrew What is your opinion? -- zhenwei pi
