diff options
author | Dan Williams <dan.j.williams@intel.com> | 2019-06-13 15:56:33 -0700 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-06-13 17:34:56 -1000 |
commit | 50f44ee7248ad2f7984ef081974a6ecd09724b3e (patch) | |
tree | ab753d9044434c94c8e6d70ead68173c2af339f6 /drivers/pci | |
parent | 1570175abd164b32ea1cc677f9dfd2dc6bd093f5 (diff) |
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 <dan.j.williams@intel.com>
Reported-by: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Logan 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/pci')
-rw-r--r-- | drivers/pci/p2pdma.c | 17 |
1 files changed, 3 insertions, 14 deletions
diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c index eecba8fbe251..a98126ad9c3a 100644 --- a/drivers/pci/p2pdma.c +++ b/drivers/pci/p2pdma.c @@ -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; |