The patch titled Subject: mm: kfence: fix PG_slab and memcg_data clearing has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-kfence-fix-pg_slab-and-memcg_data-clearing.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: Muchun Song songmuchun@bytedance.com Subject: mm: kfence: fix PG_slab and memcg_data clearing Date: Mon, 20 Mar 2023 11:00:59 +0800

It does not reset PG_slab and memcg_data when KFENCE fails to initialize kfence pool at runtime. It is reporting a "Bad page state" message when kfence pool is freed to buddy. The checking of whether it is a compound head page seems unnecessary sicne we already guarantee this when allocating kfence pool, removing the check to simplify the code.

Link: https://lkml.kernel.org/r/20230320030059.20189-1-songmuchun@bytedance.com Fixes: 0ce20dd84089 ("mm: add Kernel Electric-Fence infrastructure") Fixes: 8f0b36497303 ("mm: kfence: fix objcgs vector allocation") Signed-off-by: Muchun Song songmuchun@bytedance.com Cc: Alexander Potapenko glider@google.com Cc: Dmitry Vyukov dvyukov@google.com Cc: Jann Horn jannh@google.com Cc: Marco Elver elver@google.com Cc: Roman Gushchin roman.gushchin@linux.dev Cc: SeongJae Park sjpark@amazon.de Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

--- a/mm/kfence/core.c~mm-kfence-fix-pg_slab-and-memcg_data-clearing +++ a/mm/kfence/core.c @@ -561,10 +561,6 @@ static unsigned long kfence_init_pool(vo if (!i || (i % 2)) continue;

- /* Verify we do not have a compound head page. */ - if (WARN_ON(compound_head(&pages[i]) != &pages[i])) - return addr; - __folio_set_slab(slab_folio(slab)); #ifdef CONFIG_MEMCG slab->memcg_data = (unsigned long)&kfence_metadata[i / 2 - 1].objcg | @@ -597,12 +593,26 @@ static unsigned long kfence_init_pool(vo

/* Protect the right redzone. */ if (unlikely(!kfence_protect(addr + PAGE_SIZE))) - return addr; + goto reset_slab;

addr += 2 * PAGE_SIZE; }

return 0; + +reset_slab: + for (i = 0; i < KFENCE_POOL_SIZE / PAGE_SIZE; i++) { + struct slab *slab = page_slab(&pages[i]); + + if (!i || (i % 2)) + continue; +#ifdef CONFIG_MEMCG + slab->memcg_data = 0; +#endif + __folio_clear_slab(slab_folio(slab)); + } + + return addr; }

static bool __init kfence_init_pool_early(void) @@ -632,16 +642,6 @@ static bool __init kfence_init_pool_earl * fails for the first page, and therefore expect addr==__kfence_pool in * most failure cases. */ - for (char *p = (char *)addr; p < __kfence_pool + KFENCE_POOL_SIZE; p += PAGE_SIZE) { - struct slab *slab = virt_to_slab(p); - - if (!slab) - continue; -#ifdef CONFIG_MEMCG - slab->memcg_data = 0; -#endif - __folio_clear_slab(slab_folio(slab)); - } memblock_free_late(__pa(addr), KFENCE_POOL_SIZE - (addr - (unsigned long)__kfence_pool)); __kfence_pool = NULL; return false; _

Patches currently in -mm which might be from songmuchun@bytedance.com are

mm-kfence-fix-using-kfence_metadata-without-initialization-in-show_object.patch mm-kfence-fix-pg_slab-and-memcg_data-clearing.patch mm-hugetlb_vmemmap-simplify-hugetlb_vmemmap_init-a-bit.patch