Re: [PATCH] slub: Add back check for free nonslab objects

[Kefeng Wang]

sorry，wrong patch, please ignore

On 2021/9/27 10:09, Kefeng Wang wrote:
> After commit ("f227f0faf63b slub: fix unreclaimable slab stat for bulk
> free"), the check for free nonslab page is replaced by VM_BUG_ON_PAGE,
> which only check with CONFIG_DEBUG_VM enabled, but this config may
> impact performance, so it only for debug.
>
> Commit ("0937502af7c9 slub: Add check for kfree() of non slab objects.")
> add the ability, which should be needed in any configs to catch the
> invalid free, they even could be potential issue, eg, memory corruption,
> use after free and double free, so replace VM_BUG_ON_PAGE to WARN_ON, and
> add dump_page() to help use to debug the issue.
>
> Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
> ---
>   mm/slub.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/mm/slub.c b/mm/slub.c
> index 3095b889fab4..1bfe09098485 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -3522,7 +3522,8 @@ static inline void free_nonslab_page(struct page *page, void *object)
>   {
>   	unsigned int order = compound_order(page);
>   
> -	VM_BUG_ON_PAGE(!PageCompound(page), page);
> +	if (WARN_ON(!PageCompound(page)))
> +		dump_page(page);
>   	kfree_hook(object);
>   	mod_lruvec_page_state(page, NR_SLAB_UNRECLAIMABLE_B, -(PAGE_SIZE << order));
>   	__free_pages(page, order);