On Wed, 1 Feb 2023 15:44:33 +0800 Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> wrote:
> When the kernel copy a page from ksm_might_need_to_copy(), but runs
> into an uncorrectable error, it will crash since poisoned page is
> consumed by kernel, this is similar to the issue recently fixed by
> Copy-on-write poison recovery.
>
> When an error is detected during the page copy, return VM_FAULT_HWPOISON
> in do_swap_page(), and install a hwpoison entry in unuse_pte() when
> swapoff, which help us to avoid system crash. Note, memory failure on
> a KSM page will be skipped, but still call memory_failure_queue() to
> be consistent with general memory failure process, and we could support
> KSM page recovery in the feature.
>
Some review input would be helpful.
Are we able to identify a Fixes: target for this?
I assume that a -stable backport is desirable?
Thanks.
> --- a/mm/ksm.c
> +++ b/mm/ksm.c
> @@ -2629,8 +2629,11 @@ struct page *ksm_might_need_to_copy(struct page *page,
> new_page = NULL;
> }
> if (new_page) {
> - copy_user_highpage(new_page, page, address, vma);
> -
> + if (copy_mc_user_highpage(new_page, page, address, vma)) {
> + put_page(new_page);
> + memory_failure_queue(page_to_pfn(page), 0);
> + return ERR_PTR(-EHWPOISON);
> + }
> SetPageDirty(new_page);
> __SetPageUptodate(new_page);
> __SetPageLocked(new_page);
> diff --git a/mm/memory.c b/mm/memory.c
> index aad226daf41b..5b2c137dfb2a 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -3840,6 +3840,9 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
> if (unlikely(!page)) {
> ret = VM_FAULT_OOM;
> goto out_page;
> + } else if (unlikely(PTR_ERR(page) == -EHWPOISON)) {
> + ret = VM_FAULT_HWPOISON;
> + goto out_page;
> }
> folio = page_folio(page);
>
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 908a529bca12..3ef2468d7130 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -1763,12 +1763,15 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
> struct page *swapcache;
> spinlock_t *ptl;
> pte_t *pte, new_pte;
> + bool hwposioned = false;
> int ret = 1;
>
> swapcache = page;
> page = ksm_might_need_to_copy(page, vma, addr);
> if (unlikely(!page))
> return -ENOMEM;
> + else if (unlikely(PTR_ERR(page) == -EHWPOISON))
> + hwposioned = true;
>
> pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
> if (unlikely(!pte_same_as_swp(*pte, swp_entry_to_pte(entry)))) {
> @@ -1776,15 +1779,19 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
> goto out;
> }
>
> - if (unlikely(!PageUptodate(page))) {
> - pte_t pteval;
> + if (unlikely(hwposioned || !PageUptodate(page))) {
> + swp_entry_t swp_entry;
>
> dec_mm_counter(vma->vm_mm, MM_SWAPENTS);
> - pteval = swp_entry_to_pte(make_swapin_error_entry());
> - set_pte_at(vma->vm_mm, addr, pte, pteval);
> - swap_free(entry);
> + if (hwposioned) {
> + swp_entry = make_hwpoison_entry(swapcache);
> + page = swapcache;
> + } else {
> + swp_entry = make_swapin_error_entry();
> + }
> + new_pte = swp_entry_to_pte(swp_entry);
> ret = 0;
> - goto out;
> + goto setpte;
> }
>
> /* See do_swap_page() */
> @@ -1816,6 +1823,7 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
> new_pte = pte_mksoft_dirty(new_pte);
> if (pte_swp_uffd_wp(*pte))
> new_pte = pte_mkuffd_wp(new_pte);
> +setpte:
> set_pte_at(vma->vm_mm, addr, pte, new_pte);
> swap_free(entry);
> out:
> --
> 2.35.3
>
