From: Dan Williams <dan.j.williams@xxxxxxxxx> Subject: 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@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Fixes: 41e94a851304 ("add devm_memremap_pages") Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx> Reported-by: Logan Gunthorpe <logang@xxxxxxxxxxxx> Reviewed-by: Ira Weiny <ira.weiny@xxxxxxxxx> Reviewed-by: Logan Gunthorpe <logang@xxxxxxxxxxxx> Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> Cc: "Jérôme Glisse" <jglisse@xxxxxxxxxx> Cc: Christoph Hellwig <hch@xxxxxx> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Cc: "Rafael J. Wysocki" <rafael@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- drivers/dax/device.c | 13 +++---------- drivers/nvdimm/pmem.c | 17 +++++++++++++---- drivers/pci/p2pdma.c | 17 +++-------------- include/linux/memremap.h | 2 ++ kernel/memremap.c | 17 ++++++++++++----- mm/hmm.c | 14 +++----------- tools/testing/nvdimm/test/iomap.c | 2 ++ 7 files changed, 38 insertions(+), 44 deletions(-) --- a/drivers/dax/device.c~mm-devm_memremap_pages-fix-final-page-put-race +++ a/drivers/dax/device.c @@ -27,9 +27,8 @@ static void dev_dax_percpu_release(struc 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; --- a/drivers/nvdimm/pmem.c~mm-devm_memremap_pages-fix-final-page-put-race +++ a/drivers/nvdimm/pmem.c @@ -303,11 +303,19 @@ static const struct attribute_group *pme 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 devic 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 devic 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)); --- a/drivers/pci/p2pdma.c~mm-devm_memremap_pages-fix-final-page-put-race +++ a/drivers/pci/p2pdma.c @@ -95,7 +95,7 @@ static void pci_p2pdma_percpu_kill(struc 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_d 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_d 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_d 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; --- a/include/linux/memremap.h~mm-devm_memremap_pages-fix-final-page-put-race +++ a/include/linux/memremap.h @@ -81,6 +81,7 @@ typedef void (*dev_page_free_t)(struct p * @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; --- a/kernel/memremap.c~mm-devm_memremap_pages-fix-final-page-put-race +++ a/kernel/memremap.c @@ -95,6 +95,7 @@ static void devm_memremap_pages_release( 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( * 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 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 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 pgmap_array_delete(res); err_array: pgmap->kill(pgmap->ref); + pgmap->cleanup(pgmap->ref); + return ERR_PTR(error); } EXPORT_SYMBOL_GPL(devm_memremap_pages); --- a/mm/hmm.c~mm-devm_memremap_pages-fix-final-page-put-race +++ a/mm/hmm.c @@ -1354,9 +1354,8 @@ static void hmm_devmem_ref_release(struc complete(&devmem->completion); } -static void hmm_devmem_ref_exit(void *data) +static void hmm_devmem_ref_exit(struct percpu_ref *ref) { - struct percpu_ref *ref = data; struct hmm_devmem *devmem; devmem = container_of(ref, struct hmm_devmem, ref); @@ -1433,10 +1432,6 @@ struct hmm_devmem *hmm_devmem_add(const if (ret) return ERR_PTR(ret); - ret = devm_add_action_or_reset(device, hmm_devmem_ref_exit, &devmem->ref); - if (ret) - return ERR_PTR(ret); - size = ALIGN(size, PA_SECTION_SIZE); addr = min((unsigned long)iomem_resource.end, (1UL << MAX_PHYSMEM_BITS) - 1); @@ -1475,6 +1470,7 @@ struct hmm_devmem *hmm_devmem_add(const devmem->pagemap.ref = &devmem->ref; devmem->pagemap.data = devmem; devmem->pagemap.kill = hmm_devmem_ref_kill; + devmem->pagemap.cleanup = hmm_devmem_ref_exit; result = devm_memremap_pages(devmem->device, &devmem->pagemap); if (IS_ERR(result)) @@ -1512,11 +1508,6 @@ struct hmm_devmem *hmm_devmem_add_resour if (ret) return ERR_PTR(ret); - ret = devm_add_action_or_reset(device, hmm_devmem_ref_exit, - &devmem->ref); - if (ret) - return ERR_PTR(ret); - devmem->pfn_first = devmem->resource->start >> PAGE_SHIFT; devmem->pfn_last = devmem->pfn_first + (resource_size(devmem->resource) >> PAGE_SHIFT); @@ -1529,6 +1520,7 @@ struct hmm_devmem *hmm_devmem_add_resour devmem->pagemap.ref = &devmem->ref; devmem->pagemap.data = devmem; devmem->pagemap.kill = hmm_devmem_ref_kill; + devmem->pagemap.cleanup = hmm_devmem_ref_exit; result = devm_memremap_pages(devmem->device, &devmem->pagemap); if (IS_ERR(result)) --- a/tools/testing/nvdimm/test/iomap.c~mm-devm_memremap_pages-fix-final-page-put-race +++ a/tools/testing/nvdimm/test/iomap.c @@ -100,7 +100,9 @@ static void nfit_test_kill(void *_pgmap) { struct dev_pagemap *pgmap = _pgmap; + WARN_ON(!pgmap || !pgmap->ref || !pgmap->kill || !pgmap->cleanup); pgmap->kill(pgmap->ref); + pgmap->cleanup(pgmap->ref); } void *__wrap_devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap) _
