From dff93aba8d812930ff24c055599b60abb5aa1dab Mon Sep 17 00:00:00 2001 From: Miaohe Lin Date: Thu, 19 May 2022 20:50:26 +0800 Subject: [PATCH] mm/swapfile: unuse_pte can map random data if swap read fails Patch series "A few fixup patches for mm", v4. This series contains a few patches to avoid mapping random data if swap read fails and fix lost swap bits in unuse_pte. Also we free hwpoison and swapin error entry in madvise_free_pte_range and so on. More details can be found in the respective changelogs. This patch (of 5): There is a bug in unuse_pte(): when swap page happens to be unreadable, page filled with random data is mapped into user address space. In case of error, a special swap entry indicating swap read fails is set to the page table. So the swapcache page can be freed and the user won't end up with a permanently mounted swap because a sector is bad. And if the page is accessed later, the user process will be killed so that corrupted data is never consumed. On the other hand, if the page is never accessed, the user won't even notice it. Link: https://lkml.kernel.org/r/20220519125030.21486-1-linmiaohe@huawei.com Link: https://lkml.kernel.org/r/20220519125030.21486-2-linmiaohe@huawei.com Signed-off-by: Miaohe Lin Acked-by: David Hildenbrand Cc: Hugh Dickins Cc: Matthew Wilcox (Oracle) Cc: Vlastimil Babka Cc: David Howells Cc: NeilBrown Cc: Alistair Popple Cc: Suren Baghdasaryan Cc: Peter Xu Cc: Ralph Campbell Cc: Naoya Horiguchi Signed-off-by: Andrew Morton --- include/linux/swap.h | 7 ++++++- include/linux/swapops.h | 10 ++++++++++ mm/memory.c | 5 ++++- mm/swapfile.c | 11 +++++++++++ 4 files changed, 31 insertions(+), 2 deletions(-) diff --git a/include/linux/swap.h b/include/linux/swap.h index f3ae17b43f208..0c0fed1b348f2 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -55,6 +55,10 @@ static inline int current_is_kswapd(void) * actions on faults. */ +#define SWP_SWAPIN_ERROR_NUM 1 +#define SWP_SWAPIN_ERROR (MAX_SWAPFILES + SWP_HWPOISON_NUM + \ + SWP_MIGRATION_NUM + SWP_DEVICE_NUM + \ + SWP_PTE_MARKER_NUM) /* * PTE markers are used to persist information onto PTEs that are mapped with * file-backed memories. As its name "PTE" hints, it should only be applied to @@ -120,7 +124,8 @@ static inline int current_is_kswapd(void) #define MAX_SWAPFILES \ ((1 << MAX_SWAPFILES_SHIFT) - SWP_DEVICE_NUM - \ - SWP_MIGRATION_NUM - SWP_HWPOISON_NUM - SWP_PTE_MARKER_NUM) + SWP_MIGRATION_NUM - SWP_HWPOISON_NUM - \ + SWP_PTE_MARKER_NUM - SWP_SWAPIN_ERROR_NUM) /* * Magic header for a swap area. The first part of the union is diff --git a/include/linux/swapops.h b/include/linux/swapops.h index fe220df499f1f..f24775b418807 100644 --- a/include/linux/swapops.h +++ b/include/linux/swapops.h @@ -108,6 +108,16 @@ static inline void *swp_to_radix_entry(swp_entry_t entry) return xa_mk_value(entry.val); } +static inline swp_entry_t make_swapin_error_entry(struct page *page) +{ + return swp_entry(SWP_SWAPIN_ERROR, page_to_pfn(page)); +} + +static inline int is_swapin_error_entry(swp_entry_t entry) +{ + return swp_type(entry) == SWP_SWAPIN_ERROR; +} + #if IS_ENABLED(CONFIG_DEVICE_PRIVATE) static inline swp_entry_t make_readable_device_private_entry(pgoff_t offset) { diff --git a/mm/memory.c b/mm/memory.c index 2bf5bca39567d..54d106e0c9999 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1487,7 +1487,8 @@ again: /* Only drop the uffd-wp marker if explicitly requested */ if (!zap_drop_file_uffd_wp(details)) continue; - } else if (is_hwpoison_entry(entry)) { + } else if (is_hwpoison_entry(entry) || + is_swapin_error_entry(entry)) { if (!should_zap_cows(details)) continue; } else { @@ -3727,6 +3728,8 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) ret = vmf->page->pgmap->ops->migrate_to_ram(vmf); } else if (is_hwpoison_entry(entry)) { ret = VM_FAULT_HWPOISON; + } else if (is_swapin_error_entry(entry)) { + ret = VM_FAULT_SIGBUS; } else if (is_pte_marker_entry(entry)) { ret = handle_pte_marker(vmf); } else { diff --git a/mm/swapfile.c b/mm/swapfile.c index a0eb690d9926a..b86d1cc8d00b4 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -1788,6 +1788,17 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd, goto out; } + if (unlikely(!PageUptodate(page))) { + pte_t pteval; + + dec_mm_counter(vma->vm_mm, MM_SWAPENTS); + pteval = swp_entry_to_pte(make_swapin_error_entry(page)); + set_pte_at(vma->vm_mm, addr, pte, pteval); + swap_free(entry); + ret = 0; + goto out; + } + /* See do_swap_page() */ BUG_ON(!PageAnon(page) && PageMappedToDisk(page)); BUG_ON(PageAnon(page) && PageAnonExclusive(page)); -- 2.39.5