Re: [RFC PATCH] mm/vmalloc: fix vmalloc which may return null if called with __GFP_NOFAIL

Michal Hocko
2024-05-09T07:49:03Z

On Wed 08-05-24 20:58:08, hailong.liu@oppo.com wrote:
> From: "Hailong.Liu" <hailong.liu@oppo.com>
>
> Commit a421ef303008 ("mm: allow !GFP_KERNEL allocations for kvmalloc")
> includes support for __GFP_NOFAIL, but it presents a conflict with
> commit dd544141b9eb ("vmalloc: back off when the current task is
> OOM-killed"). A possible scenario is as belows:
>
> process-a
> kvcalloc(n, m, GFP_KERNEL | __GFP_NOFAIL)
> __vmalloc_node_range()
> __vmalloc_area_node()
> vm_area_alloc_pages()
> --> oom-killer send SIGKILL to process-a
> if (fatal_signal_pending(current)) break;
> --> return NULL;
>
> to fix this, do not check fatal_signal_pending() in vm_area_alloc_pages()
> if __GFP_NOFAIL set.
>
> Reported-by: Oven <liyangouwen1@oppo.com>
> Signed-off-by: Hailong.Liu <hailong.liu@oppo.com>
> ---
> mm/vmalloc.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 6641be0ca80b..2f359d08bf8d 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -3560,7 +3560,7 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
>
> /* High-order pages or fallback path if "bulk" fails. */
> while (nr_allocated < nr_pages) {
> - if (fatal_signal_pending(current))
> + if (!(gfp & __GFP_NOFAIL) && fatal_signal_pending(current))

Use nofail instead of gfp & __GFP_NOFAIL.

Other than that looks good to me. After that is fixed, please feel free
to add Acked-by: Michal Hocko <mhocko@suse.com>

I believe this should also have Fixes: 9376130c390a ("mm/vmalloc: add support for __GFP_NOFAIL")
--
Michal Hocko
SUSE Labs