diff options
| author | Miaohe Lin <linmiaohe@huawei.com> | 2022-04-29 14:40:43 +0800 |
|---|---|---|
| committer | akpm <akpm@linux-foundation.org> | 2022-05-27 09:33:44 -0700 |
| commit | 943fb61dd66f475c25b1ef5dddb647070f2e89a1 (patch) | |
| tree | 0f867eb3f6ae071634813a1284fa8833eb2eec4d /mm | |
| parent | 04094226d6ce8c0cb590891e13872109aa6722f1 (diff) | |
mm/z3fold: fix z3fold_page_migrate races with z3fold_map
Think about the below scenario:
CPU1 CPU2
z3fold_page_migrate z3fold_map
z3fold_page_trylock
...
z3fold_page_unlock
/* slots still points to old zhdr*/
get_z3fold_header
get slots from handle
get old zhdr from slots
z3fold_page_trylock
return *old* zhdr
encode_handle(new_zhdr, FIRST|LAST|MIDDLE)
put_page(page) /* zhdr is freed! */
but zhdr is still used by caller!
z3fold_map can map freed z3fold page and lead to use-after-free bug. To
fix it, we add PAGE_MIGRATED to indicate z3fold page is migrated and soon
to be released. So get_z3fold_header won't return such page.
Link: https://lkml.kernel.org/r/20220429064051.61552-10-linmiaohe@huawei.com
Fixes: 1f862989b04a ("mm/z3fold.c: support page migration")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/z3fold.c | 16 |
1 files changed, 12 insertions, 4 deletions
diff --git a/mm/z3fold.c b/mm/z3fold.c index a7769befd74e..f41f8b0d9e9a 100644 --- a/mm/z3fold.c +++ b/mm/z3fold.c @@ -181,6 +181,7 @@ enum z3fold_page_flags { NEEDS_COMPACTING, PAGE_STALE, PAGE_CLAIMED, /* by either reclaim or free */ + PAGE_MIGRATED, /* page is migrated and soon to be released */ }; /* @@ -270,8 +271,13 @@ static inline struct z3fold_header *get_z3fold_header(unsigned long handle) zhdr = (struct z3fold_header *)(addr & PAGE_MASK); locked = z3fold_page_trylock(zhdr); read_unlock(&slots->lock); - if (locked) - break; + if (locked) { + struct page *page = virt_to_page(zhdr); + + if (!test_bit(PAGE_MIGRATED, &page->private)) + break; + z3fold_page_unlock(zhdr); + } cpu_relax(); } while (true); } else { @@ -389,6 +395,7 @@ static struct z3fold_header *init_z3fold_page(struct page *page, bool headless, clear_bit(NEEDS_COMPACTING, &page->private); clear_bit(PAGE_STALE, &page->private); clear_bit(PAGE_CLAIMED, &page->private); + clear_bit(PAGE_MIGRATED, &page->private); if (headless) return zhdr; @@ -1576,7 +1583,7 @@ static int z3fold_page_migrate(struct address_space *mapping, struct page *newpa new_zhdr = page_address(newpage); memcpy(new_zhdr, zhdr, PAGE_SIZE); newpage->private = page->private; - page->private = 0; + set_bit(PAGE_MIGRATED, &page->private); z3fold_page_unlock(zhdr); spin_lock_init(&new_zhdr->page_lock); INIT_WORK(&new_zhdr->work, compact_page_work); @@ -1606,7 +1613,8 @@ static int z3fold_page_migrate(struct address_space *mapping, struct page *newpa queue_work_on(new_zhdr->cpu, pool->compact_wq, &new_zhdr->work); - clear_bit(PAGE_CLAIMED, &page->private); + /* PAGE_CLAIMED and PAGE_MIGRATED are cleared now. */ + page->private = 0; put_page(page); return 0; } |