The patch titled
Subject: mm/z3fold.c: fix z3fold_destroy_pool() race condition
has been added to the -mm tree. Its filename is
mm-z3foldc-fix-z3fold_destroy_pool-race-condition.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-z3foldc-fix-z3fold_destroy_pool-race-condition.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-z3foldc-fix-z3fold_destroy_pool-race-condition.patch
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------------------------------------------------------
From: Henry Burns <henryburns@xxxxxxxxxx>
Subject: mm/z3fold.c: fix z3fold_destroy_pool() race condition
The constraint from the zpool use of z3fold_destroy_pool() is there are no
outstanding handles to memory (so no active allocations), but it is
possible for there to be outstanding work on either of the two wqs in the
pool.
Calling z3fold_deregister_migration() before the workqueues are drained
means that there can be allocated pages referencing a freed inode, causing
any thread in compaction to be able to trip over the bad pointer in
PageMovable().
Link: http://lkml.kernel.org/r/20190726224810.79660-2-henryburns@xxxxxxxxxx
Fixes: 1f862989b04a ("mm/z3fold.c: support page migration")
Signed-off-by: Henry Burns <henryburns@xxxxxxxxxx>
Cc: Vitaly Vul <vitaly.vul@xxxxxxxx>
Cc: Vitaly Wool <vitalywool@xxxxxxxxx>
Cc: Shakeel Butt <shakeelb@xxxxxxxxxx>
Cc: Jonathan Adams <jwadams@xxxxxxxxxx>
Cc: David Howells <dhowells@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/z3fold.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
--- a/mm/z3fold.c~mm-z3foldc-fix-z3fold_destroy_pool-race-condition
+++ a/mm/z3fold.c
@@ -817,16 +817,19 @@ out:
static void z3fold_destroy_pool(struct z3fold_pool *pool)
{
kmem_cache_destroy(pool->c_handle);
- z3fold_unregister_migration(pool);
/*
* We need to destroy pool->compact_wq before pool->release_wq,
* as any pending work on pool->compact_wq will call
* queue_work(pool->release_wq, &pool->work).
+ *
+ * There are still outstanding pages until both workqueues are drained,
+ * so we cannot unregister migration until then.
*/
destroy_workqueue(pool->compact_wq);
destroy_workqueue(pool->release_wq);
+ z3fold_unregister_migration(pool);
kfree(pool);
}
_
Patches currently in -mm which might be from henryburns@xxxxxxxxxx are
mm-z3foldc-fix-z3fold_destroy_pool-ordering.patch
mm-z3foldc-fix-z3fold_destroy_pool-race-condition.patch
