Messages in this thread Patch in this message | | | From | Logan Gunthorpe <> | Date | Thu, 9 Feb 2023 10:29:53 -0700 | Subject | [PATCH] PCI/P2PDMA: Annotate RCU dereference |
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A dereference of the __rcu pointer was noticed by sparse:
drivers/pci/p2pdma.c:199:44: sparse: sparse: dereference of noderef expression
The __rcu pointer should be dereferenced using rcu_dereference_protected() instead of accessed directly. Its safe to use rcu_derference_protected() seeing a reference is held on the pgmap's percpu reference counter and thus it cannot disappear.
Reported-by: kernel test robot <lkp@intel.com> Signed-off-by: Logan Gunthorpe <logang@deltatee.com> ---
Based on v6.2-rc7
drivers/pci/p2pdma.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c index 86812d2073ea..9e8205572830 100644 --- a/drivers/pci/p2pdma.c +++ b/drivers/pci/p2pdma.c @@ -194,11 +194,13 @@ static const struct attribute_group p2pmem_group = { static void p2pdma_page_free(struct page *page) { struct pci_p2pdma_pagemap *pgmap = to_p2p_pgmap(page->pgmap); + /* safe to dereference while a reference is held to the percpu ref */ + struct pci_p2pdma *p2pdma = + rcu_dereference_protected(pgmap->provider->p2pdma, 1); struct percpu_ref *ref;
- gen_pool_free_owner(pgmap->provider->p2pdma->pool, - (uintptr_t)page_to_virt(page), PAGE_SIZE, - (void **)&ref); + gen_pool_free_owner(p2pdma->pool, (uintptr_t)page_to_virt(page), + PAGE_SIZE, (void **)&ref); percpu_ref_put(ref); }
base-commit: 4ec5183ec48656cec489c49f989c508b68b518e3 -- 2.30.2
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