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

[Gao Xiang]

On 2024/5/8 21:41, Gao Xiang wrote:
> +Cc Michal,
>
> On 2024/5/8 20:58, hailong.liu@xxxxxxxx wrote:
> > From: "Hailong.Liu" <hailong.liu@xxxxxxxx>
> >
> > 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@xxxxxxxx>
> > Signed-off-by: Hailong.Liu <hailong.liu@xxxxxxxx>
>
> Why taging this as RFC here?  It seems a corner-case fix of
> commit a421ef303008

BTW, I guess maybe commit e9c3cda4d86e ("mm, vmalloc: fix high order
__GFP_NOFAIL allocations") misses fatal_signal_pending() handling
anyway..

> Thanks,
> Gao Xiang