On 2022/6/4 18:32, zhenwei pi wrote:
> Currently unpoison_memory(unsigned long pfn) is designed for soft
> poison(hwpoison-inject) only. Unpoisoning a hardware corrupted page
> puts page back buddy only, 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
>
Thanks for fixing this issue.
> Signed-off-by: zhenwei pi <pizhenwei@xxxxxxxxxxxxx>
> ---
> mm/memory-failure.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index b85661cbdc4a..ec49571924f4 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,
> @@ -2101,6 +2102,13 @@ int unpoison_memory(unsigned long pfn)
> p = pfn_to_page(pfn);
> page = compound_head(p);
>
> + kpte = virt_to_kpte((unsigned long)page_to_virt(p));
> + if (kpte && !pte_present(*kpte)) {
It seems this bug is specified to x86? IIUC, not all arch will unmap the entire page if the
whole page is affected and poisoned. So the above virt_to_kpte + !pte_present check could not
detect the hardware corrupted page reliably, i.e. if page is not *whole* unmapped, e.g. *possible*
hugetlb page, we will still unpoison a hardware corrupted page. Or am I miss something?
> + unpoison_pr_info("Unpoison: Page was hardware poisoned %#lx\n",
> + pfn, &unpoison_rs);
> + return -EPERM;
> + }
> +
I think -EOPNOTSUPP might be a better error code too as Naoya pointed out.
> mutex_lock(&mf_mutex);
>
> if (!PageHWPoison(p)) {
>
Thanks!
