The patch titled
Subject: mm/z3fold: always clear PAGE_CLAIMED under z3fold page lock
has been added to the -mm mm-unstable branch. Its filename is
mm-z3fold-always-clear-page_claimed-under-z3fold-page-lock.patch
This patch should soon appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Subject: mm/z3fold: always clear PAGE_CLAIMED under z3fold page lock
Think about the below race window:
CPU1 CPU2
z3fold_reclaim_page z3fold_free
test_and_set_bit PAGE_CLAIMED
failed to reclaim page
z3fold_page_lock(zhdr);
add back to the lru list;
z3fold_page_unlock(zhdr);
get_z3fold_header
page_claimed=test_and_set_bit PAGE_CLAIMED
clear_bit(PAGE_CLAIMED, &page->private);
if (!page_claimed) /* it's false true */
free_handle is not called
free_handle won't be called in this case. So z3fold_buddy_slots will leak.
Fix it by always clear PAGE_CLAIMED under z3fold page lock.
Link: https://lkml.kernel.org/r/20220429064051.61552-8-linmiaohe@xxxxxxxxxx
Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Cc: Vitaly Wool <vitaly.wool@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/z3fold.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
--- a/mm/z3fold.c~mm-z3fold-always-clear-page_claimed-under-z3fold-page-lock
+++ a/mm/z3fold.c
@@ -1221,8 +1221,8 @@ static void z3fold_free(struct z3fold_po
return;
}
if (test_and_set_bit(NEEDS_COMPACTING, &page->private)) {
- put_z3fold_header(zhdr);
clear_bit(PAGE_CLAIMED, &page->private);
+ put_z3fold_header(zhdr);
return;
}
if (zhdr->cpu < 0 || !cpu_online(zhdr->cpu)) {
@@ -1424,8 +1424,8 @@ next:
spin_unlock(&pool->lock);
if (list_empty(&zhdr->buddy))
add_to_unbuddied(pool, zhdr);
- z3fold_page_unlock(zhdr);
clear_bit(PAGE_CLAIMED, &page->private);
+ z3fold_page_unlock(zhdr);
}
/* We started off locked to we need to lock the pool back */
@@ -1577,8 +1577,8 @@ static int z3fold_page_migrate(struct ad
if (!z3fold_page_trylock(zhdr))
return -EAGAIN;
if (zhdr->mapped_count != 0 || zhdr->foreign_handles != 0) {
- z3fold_page_unlock(zhdr);
clear_bit(PAGE_CLAIMED, &page->private);
+ z3fold_page_unlock(zhdr);
return -EBUSY;
}
if (work_pending(&zhdr->work)) {
_
Patches currently in -mm which might be from linmiaohe@xxxxxxxxxx are
mm-swapfile-unuse_pte-can-map-random-data-if-swap-read-fails.patch
mm-swapfile-fix-lost-swap-bits-in-unuse_pte.patch
mm-madvise-free-hwpoison-and-swapin-error-entry-in-madvise_free_pte_range.patch
mm-migration-reduce-the-rcu-lock-duration.patch
mm-migration-remove-unneeded-lock-page-and-pagemovable-check.patch
mm-migration-return-errno-when-isolate_huge_page-failed.patch
mm-migration-fix-potential-pte_unmap-on-an-not-mapped-pte.patch
mm-vmscan-take-min_slab_pages-into-account-when-try-to-call-shrink_node.patch
mm-vmscan-add-a-comment-about-madv_free-pages-check-in-folio_check_dirty_writeback.patch
mm-vmscan-introduce-helper-function-reclaim_page_list.patch
mm-vmscan-take-all-base-pages-of-thp-into-account-when-race-with-speculative-reference.patch
mm-vmscan-remove-obsolete-comment-in-kswapd_run.patch
mm-vmscan-use-helper-folio_is_file_lru.patch
mm-vmscan-use-helper-folio_is_file_lru-fix.patch
mm-z3fold-fix-sheduling-while-atomic.patch
mm-z3fold-fix-possible-null-pointer-dereferencing.patch
mm-z3fold-remove-buggy-use-of-stale-list-for-allocation.patch
mm-z3fold-throw-warning-on-failure-of-trylock_page-in-z3fold_alloc.patch
revert-mm-z3foldc-allow-__gfp_highmem-in-z3fold_alloc.patch
mm-z3fold-put-z3fold-page-back-into-unbuddied-list-when-reclaim-or-migration-fails.patch
mm-z3fold-always-clear-page_claimed-under-z3fold-page-lock.patch
mm-z3fold-fix-z3fold_reclaim_page-races-with-z3fold_free.patch
mm-z3fold-fix-z3fold_page_migrate-races-with-z3fold_map.patch
