The patch titled
Subject: mm/swapfile: unuse_pte can map random data if swap read fails
has been added to the -mm tree. Its filename is
mm-swapfile-unuse_pte-can-map-random-data-if-swap-read-fails.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-swapfile-unuse_pte-can-map-random-data-if-swap-read-fails.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-swapfile-unuse_pte-can-map-random-data-if-swap-read-fails.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Subject: mm/swapfile: unuse_pte can map random data if swap read fails
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/20220416030549.60559-1-linmiaohe@xxxxxxxxxx
Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: David Howells <dhowells@xxxxxxxxxx>
Cc: NeilBrown <neilb@xxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Alistair Popple <apopple@xxxxxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
Cc: Ralph Campbell <rcampbell@xxxxxxxxxx>
Cc: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
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(-)
--- a/include/linux/swap.h~mm-swapfile-unuse_pte-can-map-random-data-if-swap-read-fails
+++ a/include/linux/swap.h
@@ -55,6 +55,10 @@ static inline int current_is_kswapd(void
* actions on faults.
*/
+#define SWAP_READ_ERROR_NUM 1
+#define SWAP_READ_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 - SWAP_READ_ERROR_NUM)
/*
* Magic header for a swap area. The first part of the union is
--- a/include/linux/swapops.h~mm-swapfile-unuse_pte-can-map-random-data-if-swap-read-fails
+++ a/include/linux/swapops.h
@@ -108,6 +108,16 @@ static inline void *swp_to_radix_entry(s
return xa_mk_value(entry.val);
}
+static inline swp_entry_t make_swapin_error_entry(struct page *page)
+{
+ return swp_entry(SWAP_READ_ERROR, page_to_pfn(page));
+}
+
+static inline int is_swapin_error_entry(swp_entry_t entry)
+{
+ return swp_type(entry) == SWAP_READ_ERROR;
+}
+
#if IS_ENABLED(CONFIG_DEVICE_PRIVATE)
static inline swp_entry_t make_readable_device_private_entry(pgoff_t offset)
{
--- a/mm/memory.c~mm-swapfile-unuse_pte-can-map-random-data-if-swap-read-fails
+++ a/mm/memory.c
@@ -1485,7 +1485,8 @@ 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 {
@@ -3731,6 +3732,8 @@ vm_fault_t do_swap_page(struct vm_fault
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 {
--- a/mm/swapfile.c~mm-swapfile-unuse_pte-can-map-random-data-if-swap-read-fails
+++ a/mm/swapfile.c
@@ -1797,6 +1797,17 @@ static int unuse_pte(struct vm_area_stru
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));
_
Patches currently in -mm which might be from linmiaohe@xxxxxxxxxx are
mm-shmem-make-shmem_init-return-void.patch
mm-memcg-remove-unneeded-nr_scanned.patch
mm-mmapc-use-helper-mlock_future_check.patch
mm-mremap-use-helper-mlock_future_check.patch
mm-mremap-avoid-unneeded-do_munmap-call.patch
mm-memory-failurec-minor-cleanup-for-hwpoisonhandlable.patch
mm-memory-failurec-dissolve-truncated-hugetlb-page.patch
mm-vmscan-remove-obsolete-comment-in-get_scan_count.patch
mm-vmscan-fix-comment-for-current_may_throttle.patch
mm-z3fold-declare-z3fold_mount-with-__init.patch
mm-z3fold-remove-obsolete-comment-in-z3fold_alloc.patch
mm-z3fold-minor-clean-up-for-z3fold_free.patch
mm-z3fold-remove-unneeded-page_mapcount_reset-and-clearpageprivate.patch
mm-z3fold-remove-confusing-local-variable-l-reassignment.patch
mm-z3fold-move-decrement-of-pool-pages_nr-into-__release_z3fold_page.patch
mm-z3fold-remove-redundant-list_del_init-of-zhdr-buddy-in-z3fold_free.patch
mm-z3fold-remove-unneeded-page_headless-check-in-free_handle.patch
mm-compaction-use-helper-isolation_suitable.patch
drivers-base-nodec-fix-compaction-sysfs-file-leak.patch
mm-migration-remove-unneeded-local-variable-mapping_locked.patch
mm-migration-remove-unneeded-local-variable-page_lru.patch
mm-migration-use-helper-function-vma_lookup-in-add_page_for_migration.patch
mm-migration-use-helper-macro-min-in-do_pages_stat.patch
mm-migration-avoid-unneeded-nodemask_t-initialization.patch
mm-migration-remove-some-duplicated-codes-in-migrate_pages.patch
mm-migration-fix-potential-page-refcounts-leak-in-migrate_pages.patch
mm-migration-fix-potential-invalid-node-access-for-reclaim-based-migration.patch
mm-migration-fix-possible-do_pages_stat_array-racing-with-memory-offline.patch
mm-madvise-fix-potential-pte_unmap_unlock-pte-error.patch
mm-compaction-remove-unneeded-return-value-of-kcompactd_run.patch
mm-compaction-remove-unneeded-pfn-update.patch
mm-compaction-remove-unneeded-assignment-to-isolate_start_pfn.patch
mm-compaction-clean-up-comment-for-sched-contention.patch
mm-compaction-clean-up-comment-about-suitable-migration-target-recheck.patch
mm-compaction-use-compact_cluster_max-in-compactionc.patch
mm-compaction-use-helper-compound_nr-in-isolate_migratepages_block.patch
mm-compaction-clean-up-comment-about-async-compaction-in-isolate_migratepages.patch
mm-compaction-avoid-possible-null-pointer-dereference-in-kcompactd_cpu_online.patch
mm-compaction-make-compaction_zonelist_suitable-return-false-when-compact_success.patch
mm-compaction-simplify-the-code-in-__compact_finished.patch
mm-compaction-make-sure-highest-is-above-the-min_pfn.patch
mm-swapfile-unuse_pte-can-map-random-data-if-swap-read-fails.patch
