From 50f44ee7248ad2f7984ef081974a6ecd09724b3e Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Thu, 13 Jun 2019 15:56:33 -0700 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@dwillia2-desk3.amr.corp.intel.com Fixes: 41e94a851304 ("add devm_memremap_pages") Signed-off-by: Dan Williams Reported-by: Logan Gunthorpe Reviewed-by: Ira Weiny Reviewed-by: Logan Gunthorpe Cc: Bjorn Helgaas Cc: "Jérôme Glisse" Cc: Christoph Hellwig Cc: Greg Kroah-Hartman Cc: "Rafael J. Wysocki" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/memremap.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) (limited to 'kernel/memremap.c') diff --git a/kernel/memremap.c b/kernel/memremap.c index 715b434bd316..6e1970719dc2 100644 --- a/kernel/memremap.c +++ b/kernel/memremap.c @@ -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); -- cgit v1.2.3-55-g7522