From: Muchun Song songmuchun@bytedance.com
commit 1f2803b2660f4b04d48d065072c0ae0c9ca255fd upstream.
The struct pages could be discontiguous when the kfence pool is allocated via alloc_contig_pages() with CONFIG_SPARSEMEM and !CONFIG_SPARSEMEM_VMEMMAP.
This may result in setting PG_slab and memcg_data to a arbitrary address (may be not used as a struct page), which in the worst case might corrupt the kernel.
So the iteration should use nth_page().
Link: https://lkml.kernel.org/r/20230323025003.94447-1-songmuchun@bytedance.com Fixes: 0ce20dd84089 ("mm: add Kernel Electric-Fence infrastructure") Signed-off-by: Muchun Song songmuchun@bytedance.com Reviewed-by: Marco Elver elver@google.com Reviewed-by: Kefeng Wang wangkefeng.wang@huawei.com Cc: Alexander Potapenko glider@google.com Cc: Dmitry Vyukov dvyukov@google.com Cc: Jann Horn jannh@google.com Cc: SeongJae Park sjpark@amazon.de Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/kfence/core.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/mm/kfence/core.c +++ b/mm/kfence/core.c @@ -556,7 +556,7 @@ static unsigned long kfence_init_pool(vo * enters __slab_free() slow-path. */ for (i = 0; i < KFENCE_POOL_SIZE / PAGE_SIZE; i++) { - struct slab *slab = page_slab(&pages[i]); + struct slab *slab = page_slab(nth_page(pages, i));
if (!i || (i % 2)) continue; @@ -602,7 +602,7 @@ static unsigned long kfence_init_pool(vo
reset_slab: for (i = 0; i < KFENCE_POOL_SIZE / PAGE_SIZE; i++) { - struct slab *slab = page_slab(&pages[i]); + struct slab *slab = page_slab(nth_page(pages, i));
if (!i || (i % 2)) continue;