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

Gao Xiang
2024-05-08T14:13:50Z

On 2024/5/8 21:41, Gao Xiang wrote:
>
> +Cc Michal,
>
> On 2024/5/8 20:58, 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>
>
> 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
>