We want to get rid of nth_page(), and kfence init code is the last user.
Unfortunately, we might actually walk a PFN range where the pages are not contiguous, because we might be allocating an area from memblock that could span memory sections in problematic kernel configs (SPARSEMEM without SPARSEMEM_VMEMMAP).
We could check whether the page range is contiguous using page_range_contiguous() and failing kfence init, or making kfence incompatible these problemtic kernel configs.
Let's keep it simple and simply use pfn_to_page() by iterating PFNs.
Reviewed-by: Marco Elver elver@google.com Reviewed-by: Lorenzo Stoakes lorenzo.stoakes@oracle.com Cc: Alexander Potapenko glider@google.com Cc: Dmitry Vyukov dvyukov@google.com Signed-off-by: David Hildenbrand david@redhat.com --- mm/kfence/core.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/mm/kfence/core.c b/mm/kfence/core.c index 0ed3be100963a..727c20c94ac59 100644 --- a/mm/kfence/core.c +++ b/mm/kfence/core.c @@ -594,15 +594,14 @@ static void rcu_guarded_free(struct rcu_head *h) */ static unsigned long kfence_init_pool(void) { - unsigned long addr; - struct page *pages; + unsigned long addr, start_pfn; int i;
if (!arch_kfence_init_pool()) return (unsigned long)__kfence_pool;
addr = (unsigned long)__kfence_pool; - pages = virt_to_page(__kfence_pool); + start_pfn = PHYS_PFN(virt_to_phys(__kfence_pool));
/* * Set up object pages: they must have PGTY_slab set to avoid freeing @@ -613,11 +612,12 @@ static unsigned long kfence_init_pool(void) * enters __slab_free() slow-path. */ for (i = 0; i < KFENCE_POOL_SIZE / PAGE_SIZE; i++) { - struct slab *slab = page_slab(nth_page(pages, i)); + struct slab *slab;
if (!i || (i % 2)) continue;
+ slab = page_slab(pfn_to_page(start_pfn + i)); __folio_set_slab(slab_folio(slab)); #ifdef CONFIG_MEMCG slab->obj_exts = (unsigned long)&kfence_metadata_init[i / 2 - 1].obj_exts | @@ -665,10 +665,12 @@ static unsigned long kfence_init_pool(void)
reset_slab: for (i = 0; i < KFENCE_POOL_SIZE / PAGE_SIZE; i++) { - struct slab *slab = page_slab(nth_page(pages, i)); + struct slab *slab;
if (!i || (i % 2)) continue; + + slab = page_slab(pfn_to_page(start_pfn + i)); #ifdef CONFIG_MEMCG slab->obj_exts = 0; #endif