* [PATCH] mm/z3fold.c: Fix z3fold_destroy_pool() race condition
2019-07-26 22:48 [PATCH] mm/z3fold.c: Fix z3fold_destroy_pool() ordering Henry Burns
@ 2019-07-26 22:48 ` Henry Burns
2019-07-26 23:07 ` Shakeel Butt
2019-07-26 23:20 ` Jonathan Adams
2019-07-26 22:53 ` [PATCH] mm/z3fold.c: Fix z3fold_destroy_pool() ordering Shakeel Butt
2019-07-26 23:19 ` Jonathan Adams
2 siblings, 2 replies; 8+ messages in thread
From: Henry Burns @ 2019-07-26 22:48 UTC (permalink / raw)
To: Vitaly Vul
Cc: Andrew Morton, Shakeel Butt, Jonathan Adams, David Howells,
Thomas Gleixner, Al Viro, linux-mm, linux-kernel, Henry Burns,
stable
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().
Fixes: 1f862989b04a ("mm/z3fold.c: support page migration")
Signed-off-by: Henry Burns <henryburns@google.com>
Cc: <stable@vger.kernel.org>
---
mm/z3fold.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/mm/z3fold.c b/mm/z3fold.c
index 43de92f52961..ed19d98c9dcd 100644
--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -817,16 +817,19 @@ static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp,
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);
}
--
2.22.0.709.g102302147b-goog
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [PATCH] mm/z3fold.c: Fix z3fold_destroy_pool() race condition
2019-07-26 22:48 ` [PATCH] mm/z3fold.c: Fix z3fold_destroy_pool() race condition Henry Burns
@ 2019-07-26 23:07 ` Shakeel Butt
2019-07-26 23:20 ` Jonathan Adams
1 sibling, 0 replies; 8+ messages in thread
From: Shakeel Butt @ 2019-07-26 23:07 UTC (permalink / raw)
To: Henry Burns
Cc: Vitaly Vul, Andrew Morton, Jonathan Adams, David Howells,
Thomas Gleixner, Al Viro, Linux MM, LKML, stable
On Fri, Jul 26, 2019 at 3:48 PM Henry Burns <henryburns@google.com> wrote:
>
> 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().
>
> Fixes: 1f862989b04a ("mm/z3fold.c: support page migration")
>
> Signed-off-by: Henry Burns <henryburns@google.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
> Cc: <stable@vger.kernel.org>
> ---
> mm/z3fold.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/mm/z3fold.c b/mm/z3fold.c
> index 43de92f52961..ed19d98c9dcd 100644
> --- a/mm/z3fold.c
> +++ b/mm/z3fold.c
> @@ -817,16 +817,19 @@ static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp,
> 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);
> }
>
> --
> 2.22.0.709.g102302147b-goog
>
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [PATCH] mm/z3fold.c: Fix z3fold_destroy_pool() race condition
2019-07-26 22:48 ` [PATCH] mm/z3fold.c: Fix z3fold_destroy_pool() race condition Henry Burns
2019-07-26 23:07 ` Shakeel Butt
@ 2019-07-26 23:20 ` Jonathan Adams
2019-07-29 18:41 ` Henry Burns
1 sibling, 1 reply; 8+ messages in thread
From: Jonathan Adams @ 2019-07-26 23:20 UTC (permalink / raw)
To: Henry Burns
Cc: Vitaly Vul, Andrew Morton, Shakeel Butt, David Howells,
Thomas Gleixner, Al Viro, Linux-MM, LKML, stable
On Fri, Jul 26, 2019 at 3:48 PM Henry Burns <henryburns@google.com> wrote:
>
> 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().
>
> Fixes: 1f862989b04a ("mm/z3fold.c: support page migration")
>
> Signed-off-by: Henry Burns <henryburns@google.com>
Reviewed-by: Jonathan Adams <jwadams@google.com>
> Cc: <stable@vger.kernel.org>
> ---
> mm/z3fold.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/mm/z3fold.c b/mm/z3fold.c
> index 43de92f52961..ed19d98c9dcd 100644
> --- a/mm/z3fold.c
> +++ b/mm/z3fold.c
> @@ -817,16 +817,19 @@ static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp,
> 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);
> }
>
> --
> 2.22.0.709.g102302147b-goog
>
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [PATCH] mm/z3fold.c: Fix z3fold_destroy_pool() race condition
2019-07-26 23:20 ` Jonathan Adams
@ 2019-07-29 18:41 ` Henry Burns
0 siblings, 0 replies; 8+ messages in thread
From: Henry Burns @ 2019-07-29 18:41 UTC (permalink / raw)
To: Jonathan Adams
Cc: Vitaly Vul, Andrew Morton, Shakeel Butt, David Howells,
Thomas Gleixner, Al Viro, Linux-MM, LKML, stable
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().
Fixes: 1f862989b04a ("mm/z3fold.c: support page migration")
Signed-off-by: Henry Burns <henryburns@google.com>
> Reviewed-by: Shakeel Butt <shakeelb@google.com>
> Reviewed-by: Jonathan Adams <jwadams@google.com>
>
> > Cc: <stable@vger.kernel.org>
> > ---
> > mm/z3fold.c | 5 ++++-
> > 1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/mm/z3fold.c b/mm/z3fold.c
> > index 43de92f52961..ed19d98c9dcd 100644
> > --- a/mm/z3fold.c
> > +++ b/mm/z3fold.c
> > @@ -817,16 +817,19 @@ static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp,
> > 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);
> > }
> >
> > --
> > 2.22.0.709.g102302147b-goog
> >
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] mm/z3fold.c: Fix z3fold_destroy_pool() ordering
2019-07-26 22:48 [PATCH] mm/z3fold.c: Fix z3fold_destroy_pool() ordering Henry Burns
2019-07-26 22:48 ` [PATCH] mm/z3fold.c: Fix z3fold_destroy_pool() race condition Henry Burns
@ 2019-07-26 22:53 ` Shakeel Butt
2019-07-26 23:19 ` Jonathan Adams
2 siblings, 0 replies; 8+ messages in thread
From: Shakeel Butt @ 2019-07-26 22:53 UTC (permalink / raw)
To: Henry Burns
Cc: Vitaly Vul, Andrew Morton, Jonathan Adams, David Howells,
Thomas Gleixner, Al Viro, Linux MM, LKML, stable
On Fri, Jul 26, 2019 at 3:48 PM Henry Burns <henryburns@google.com> wrote:
>
> 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.
>
> If there is work queued on pool->compact_workqueue when it is called,
> z3fold_destroy_pool() will do:
>
> z3fold_destroy_pool()
> destroy_workqueue(pool->release_wq)
> destroy_workqueue(pool->compact_wq)
> drain_workqueue(pool->compact_wq)
> do_compact_page(zhdr)
> kref_put(&zhdr->refcount)
> __release_z3fold_page(zhdr, ...)
> queue_work_on(pool->release_wq, &pool->work) *BOOM*
>
> So compact_wq needs to be destroyed before release_wq.
>
> Fixes: 5d03a6613957 ("mm/z3fold.c: use kref to prevent page free/compact race")
>
> Signed-off-by: Henry Burns <henryburns@google.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
> Cc: <stable@vger.kernel.org>
> ---
> mm/z3fold.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/mm/z3fold.c b/mm/z3fold.c
> index 1a029a7432ee..43de92f52961 100644
> --- a/mm/z3fold.c
> +++ b/mm/z3fold.c
> @@ -818,8 +818,15 @@ static void z3fold_destroy_pool(struct z3fold_pool *pool)
> {
> kmem_cache_destroy(pool->c_handle);
> z3fold_unregister_migration(pool);
> - destroy_workqueue(pool->release_wq);
> +
> + /*
> + * 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).
> + */
> +
> destroy_workqueue(pool->compact_wq);
> + destroy_workqueue(pool->release_wq);
> kfree(pool);
> }
>
> --
> 2.22.0.709.g102302147b-goog
>
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [PATCH] mm/z3fold.c: Fix z3fold_destroy_pool() ordering
2019-07-26 22:48 [PATCH] mm/z3fold.c: Fix z3fold_destroy_pool() ordering Henry Burns
2019-07-26 22:48 ` [PATCH] mm/z3fold.c: Fix z3fold_destroy_pool() race condition Henry Burns
2019-07-26 22:53 ` [PATCH] mm/z3fold.c: Fix z3fold_destroy_pool() ordering Shakeel Butt
@ 2019-07-26 23:19 ` Jonathan Adams
2019-07-29 18:38 ` Henry Burns
2 siblings, 1 reply; 8+ messages in thread
From: Jonathan Adams @ 2019-07-26 23:19 UTC (permalink / raw)
To: Henry Burns
Cc: Vitaly Vul, Andrew Morton, Shakeel Butt, David Howells,
Thomas Gleixner, Al Viro, Linux-MM, LKML, stable
On Fri, Jul 26, 2019 at 3:48 PM Henry Burns <henryburns@google.com> wrote:
>
> 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.
>
> If there is work queued on pool->compact_workqueue when it is called,
> z3fold_destroy_pool() will do:
>
> z3fold_destroy_pool()
> destroy_workqueue(pool->release_wq)
> destroy_workqueue(pool->compact_wq)
> drain_workqueue(pool->compact_wq)
> do_compact_page(zhdr)
> kref_put(&zhdr->refcount)
> __release_z3fold_page(zhdr, ...)
> queue_work_on(pool->release_wq, &pool->work) *BOOM*
>
> So compact_wq needs to be destroyed before release_wq.
>
> Fixes: 5d03a6613957 ("mm/z3fold.c: use kref to prevent page free/compact race")
>
> Signed-off-by: Henry Burns <henryburns@google.com>
Reviewed-by: Jonathan Adams <jwadams@google.com>
> Cc: <stable@vger.kernel.org>
> ---
> mm/z3fold.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/mm/z3fold.c b/mm/z3fold.c
> index 1a029a7432ee..43de92f52961 100644
> --- a/mm/z3fold.c
> +++ b/mm/z3fold.c
> @@ -818,8 +818,15 @@ static void z3fold_destroy_pool(struct z3fold_pool *pool)
> {
> kmem_cache_destroy(pool->c_handle);
> z3fold_unregister_migration(pool);
> - destroy_workqueue(pool->release_wq);
> +
> + /*
> + * 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).
> + */
> +
> destroy_workqueue(pool->compact_wq);
> + destroy_workqueue(pool->release_wq);
> kfree(pool);
> }
>
> --
> 2.22.0.709.g102302147b-goog
>
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [PATCH] mm/z3fold.c: Fix z3fold_destroy_pool() ordering
2019-07-26 23:19 ` Jonathan Adams
@ 2019-07-29 18:38 ` Henry Burns
0 siblings, 0 replies; 8+ messages in thread
From: Henry Burns @ 2019-07-29 18:38 UTC (permalink / raw)
To: Jonathan Adams
Cc: Vitaly Vul, Andrew Morton, Shakeel Butt, David Howells,
Thomas Gleixner, Al Viro, Linux-MM, LKML, stable
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.
If there is work queued on pool->compact_workqueue when it is called,
z3fold_destroy_pool() will do:
z3fold_destroy_pool()
destroy_workqueue(pool->release_wq)
destroy_workqueue(pool->compact_wq)
drain_workqueue(pool->compact_wq)
do_compact_page(zhdr)
kref_put(&zhdr->refcount)
__release_z3fold_page(zhdr, ...)
queue_work_on(pool->release_wq, &pool->work) *BOOM*
So compact_wq needs to be destroyed before release_wq.
Fixes: 5d03a6613957 ("mm/z3fold.c: use kref to prevent page free/compact race")
Signed-off-by: Henry Burns <henryburns@google.com>
> Reviewed-by: Shakeel Butt <shakeelb@google.com>
> Reviewed-by: Jonathan Adams <jwadams@google.com>
>
> > Cc: <stable@vger.kernel.org>
> > ---
> > mm/z3fold.c | 9 ++++++++-
> > 1 file changed, 8 insertions(+), 1 deletion(-)
> >
> > diff --git a/mm/z3fold.c b/mm/z3fold.c
> > index 1a029a7432ee..43de92f52961 100644
> > --- a/mm/z3fold.c
> > +++ b/mm/z3fold.c
> > @@ -818,8 +818,15 @@ static void z3fold_destroy_pool(struct z3fold_pool *pool)
> > {
> > kmem_cache_destroy(pool->c_handle);
> > z3fold_unregister_migration(pool);
> > - destroy_workqueue(pool->release_wq);
> > +
> > + /*
> > + * 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).
> > + */
> > +
> > destroy_workqueue(pool->compact_wq);
> > + destroy_workqueue(pool->release_wq);
> > kfree(pool);
> > }
> >
> > --
> > 2.22.0.709.g102302147b-goog
> >
^ permalink raw reply [flat|nested] 8+ messages in thread