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Commit 50f44ee7 authored by Dan Williams's avatar Dan Williams Committed by Linus Torvalds
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mm/devm_memremap_pages: fix final page put race 

Logan noticed that devm_memremap_pages_release() kills the percpu_ref
drops all the page references that were acquired at init and then
immediately proceeds to unplug, arch_remove_memory(), the backing pages
for the pagemap.  If for some reason device shutdown actually collides
with a busy / elevated-ref-count page then arch_remove_memory() should
be deferred until after that reference is dropped.

As it stands the "wait for last page ref drop" happens *after*
devm_memremap_pages_release() returns, which is obviously too late and
can lead to crashes.

Fix this situation by assigning the responsibility to wait for the
percpu_ref to go idle to devm_memremap_pages() with a new ->cleanup()
callback.  Implement the new cleanup callback for all
devm_memremap_pages() users: pmem, devdax, hmm, and p2pdma.

Link: http://lkml.kernel.org/r/155727339156.292046.5432007428235387859.stgit@dwillia2-desk3.amr.corp.intel.com


Fixes: 41e94a85 ("add devm_memremap_pages")
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
Reported-by: default avatarLogan Gunthorpe <logang@deltatee.com>
Reviewed-by: default avatarIra Weiny <ira.weiny@intel.com>
Reviewed-by: default avatarLogan Gunthorpe <logang@deltatee.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: "Jérôme Glisse" <jglisse@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 1570175a

drivers/dax/device.c

+3 −10
Original line number Diff line number Diff line
@@ -27,9 +27,8 @@ static void dev_dax_percpu_release(struct percpu_ref *ref) 
	complete(&dev_dax->cmp);

}



static void dev_dax_percpu_exit(void *data)

static void dev_dax_percpu_exit(struct percpu_ref *ref)

{

	struct percpu_ref *ref = data;

	struct dev_dax *dev_dax = ref_to_dev_dax(ref);



	dev_dbg(&dev_dax->dev, "%s\n", __func__);
@@ -466,18 +465,12 @@ int dev_dax_probe(struct device *dev) 
	if (rc)

		return rc;



	rc = devm_add_action_or_reset(dev, dev_dax_percpu_exit, &dev_dax->ref);

	if (rc)

		return rc;



	dev_dax->pgmap.ref = &dev_dax->ref;

	dev_dax->pgmap.kill = dev_dax_percpu_kill;

	dev_dax->pgmap.cleanup = dev_dax_percpu_exit;

	addr = devm_memremap_pages(dev, &dev_dax->pgmap);

	if (IS_ERR(addr)) {

		devm_remove_action(dev, dev_dax_percpu_exit, &dev_dax->ref);

		percpu_ref_exit(&dev_dax->ref);

	if (IS_ERR(addr))

		return PTR_ERR(addr);

	}



	inode = dax_inode(dax_dev);

	cdev = inode->i_cdev;

drivers/nvdimm/pmem.c

+13 −4
Original line number Diff line number Diff line
@@ -303,11 +303,19 @@ static const struct attribute_group *pmem_attribute_groups[] = { 
	NULL,

};



static void pmem_release_queue(void *q)

static void __pmem_release_queue(struct percpu_ref *ref)

{

	struct request_queue *q;



	q = container_of(ref, typeof(*q), q_usage_counter);

	blk_cleanup_queue(q);

}



static void pmem_release_queue(void *ref)

{

	__pmem_release_queue(ref);

}



static void pmem_freeze_queue(struct percpu_ref *ref)

{

	struct request_queue *q;
@@ -399,12 +407,10 @@ static int pmem_attach_disk(struct device *dev, 
	if (!q)

		return -ENOMEM;



	if (devm_add_action_or_reset(dev, pmem_release_queue, q))

		return -ENOMEM;



	pmem->pfn_flags = PFN_DEV;

	pmem->pgmap.ref = &q->q_usage_counter;

	pmem->pgmap.kill = pmem_freeze_queue;

	pmem->pgmap.cleanup = __pmem_release_queue;

	if (is_nd_pfn(dev)) {

		if (setup_pagemap_fsdax(dev, &pmem->pgmap))

			return -ENOMEM;
@@ -425,6 +431,9 @@ static int pmem_attach_disk(struct device *dev, 
		pmem->pfn_flags |= PFN_MAP;

		memcpy(&bb_res, &pmem->pgmap.res, sizeof(bb_res));

	} else {

		if (devm_add_action_or_reset(dev, pmem_release_queue,

					&q->q_usage_counter))

			return -ENOMEM;

		addr = devm_memremap(dev, pmem->phys_addr,

				pmem->size, ARCH_MEMREMAP_PMEM);

		memcpy(&bb_res, &nsio->res, sizeof(bb_res));

drivers/pci/p2pdma.c

+3 −14
Original line number Diff line number Diff line
@@ -95,7 +95,7 @@ static void pci_p2pdma_percpu_kill(struct percpu_ref *ref) 
	percpu_ref_kill(ref);

}



static void pci_p2pdma_percpu_cleanup(void *ref)

static void pci_p2pdma_percpu_cleanup(struct percpu_ref *ref)

{

	struct p2pdma_pagemap *p2p_pgmap = to_p2p_pgmap(ref);
@@ -198,16 +198,6 @@ int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar, size_t size, 
	if (error)

		goto pgmap_free;



	/*

	 * FIXME: the percpu_ref_exit needs to be coordinated internal

	 * to devm_memremap_pages_release(). Duplicate the same ordering

	 * as other devm_memremap_pages() users for now.

	 */

	error = devm_add_action(&pdev->dev, pci_p2pdma_percpu_cleanup,

			&p2p_pgmap->ref);

	if (error)

		goto ref_cleanup;



	pgmap = &p2p_pgmap->pgmap;



	pgmap->res.start = pci_resource_start(pdev, bar) + offset;
@@ -218,11 +208,12 @@ int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar, size_t size, 
	pgmap->pci_p2pdma_bus_offset = pci_bus_address(pdev, bar) -

		pci_resource_start(pdev, bar);

	pgmap->kill = pci_p2pdma_percpu_kill;

	pgmap->cleanup = pci_p2pdma_percpu_cleanup;



	addr = devm_memremap_pages(&pdev->dev, pgmap);

	if (IS_ERR(addr)) {

		error = PTR_ERR(addr);

		goto ref_exit;

		goto pgmap_free;

	}



	error = gen_pool_add_owner(pdev->p2pdma->pool, (unsigned long)addr,
@@ -239,8 +230,6 @@ int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar, size_t size, 


pages_free:

	devm_memunmap_pages(&pdev->dev, pgmap);

ref_cleanup:

	percpu_ref_exit(&p2p_pgmap->ref);

pgmap_free:

	devm_kfree(&pdev->dev, p2p_pgmap);

	return error;

include/linux/memremap.h

+2 −0
Original line number Diff line number Diff line
@@ -81,6 +81,7 @@ typedef void (*dev_page_free_t)(struct page *page, void *data); 
 * @res: physical address range covered by @ref

 * @ref: reference count that pins the devm_memremap_pages() mapping

 * @kill: callback to transition @ref to the dead state

 * @cleanup: callback to wait for @ref to be idle and reap it

 * @dev: host device of the mapping for debug

 * @data: private data pointer for page_free()

 * @type: memory type: see MEMORY_* in memory_hotplug.h
@@ -92,6 +93,7 @@ struct dev_pagemap { 
	struct resource res;

	struct percpu_ref *ref;

	void (*kill)(struct percpu_ref *ref);

	void (*cleanup)(struct percpu_ref *ref);

	struct device *dev;

	void *data;

	enum memory_type type;

kernel/memremap.c

+12 −5
Original line number Diff line number Diff line
@@ -95,6 +95,7 @@ static void devm_memremap_pages_release(void *data) 
	pgmap->kill(pgmap->ref);

	for_each_device_pfn(pfn, pgmap)

		put_page(pfn_to_page(pfn));

	pgmap->cleanup(pgmap->ref);



	/* pages are dead and unused, undo the arch mapping */

	align_start = res->start & ~(SECTION_SIZE - 1);
@@ -133,8 +134,8 @@ static void devm_memremap_pages_release(void *data) 
 * 2/ The altmap field may optionally be initialized, in which case altmap_valid

 *    must be set to true

 *

 * 3/ pgmap->ref must be 'live' on entry and will be killed at

 *    devm_memremap_pages_release() time, or if this routine fails.

 * 3/ pgmap->ref must be 'live' on entry and will be killed and reaped

 *    at devm_memremap_pages_release() time, or if this routine fails.

 *

 * 4/ res is expected to be a host memory range that could feasibly be

 *    treated as a "System RAM" range, i.e. not a device mmio range, but
@@ -156,8 +157,10 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap) 
	pgprot_t pgprot = PAGE_KERNEL;

	int error, nid, is_ram;



	if (!pgmap->ref || !pgmap->kill)

	if (!pgmap->ref || !pgmap->kill || !pgmap->cleanup) {

		WARN(1, "Missing reference count teardown definition\n");

		return ERR_PTR(-EINVAL);

	}



	align_start = res->start & ~(SECTION_SIZE - 1);

	align_size = ALIGN(res->start + resource_size(res), SECTION_SIZE)
@@ -168,14 +171,16 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap) 
	if (conflict_pgmap) {

		dev_WARN(dev, "Conflicting mapping in same section\n");

		put_dev_pagemap(conflict_pgmap);

		return ERR_PTR(-ENOMEM);

		error = -ENOMEM;

		goto err_array;

	}



	conflict_pgmap = get_dev_pagemap(PHYS_PFN(align_end), NULL);

	if (conflict_pgmap) {

		dev_WARN(dev, "Conflicting mapping in same section\n");

		put_dev_pagemap(conflict_pgmap);

		return ERR_PTR(-ENOMEM);

		error = -ENOMEM;

		goto err_array;

	}



	is_ram = region_intersects(align_start, align_size,
@@ -267,6 +272,8 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap) 
	pgmap_array_delete(res);

 err_array:

	pgmap->kill(pgmap->ref);

	pgmap->cleanup(pgmap->ref);



	return ERR_PTR(error);

}

EXPORT_SYMBOL_GPL(devm_memremap_pages);