From: Muchun Song <songmuchun@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxx Fixes: 0ce20dd84089 ("mm: add Kernel Electric-Fence infrastructure") Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx> Reviewed-by: Marco Elver <elver@xxxxxxxxxx> Reviewed-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> Cc: Alexander Potapenko <glider@xxxxxxxxxx> Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Cc: Jann Horn <jannh@xxxxxxxxxx> Cc: SeongJae Park <sjpark@xxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- 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;
