linux-kernel - Re: [PATCH 09/41] mm: rcu safe VMA freeing

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Message-ID: <Y8av6HjRUvaujeEO@dhcp22.suse.cz>
Date:   Tue, 17 Jan 2023 15:25:44 +0100
From:   Michal Hocko <mhocko@...e.com>
To:     Suren Baghdasaryan <surenb@...gle.com>
Cc:     akpm@...ux-foundation.org, michel@...pinasse.org,
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Subject: Re: [PATCH 09/41] mm: rcu safe VMA freeing

On Mon 09-01-23 12:53:04, Suren Baghdasaryan wrote:
[...]
>  void vm_area_free(struct vm_area_struct *vma)
>  {
>  	free_anon_vma_name(vma);
> +#ifdef CONFIG_PER_VMA_LOCK
> +	call_rcu(&vma->vm_rcu, __vm_area_free);
> +#else
>  	kmem_cache_free(vm_area_cachep, vma);
> +#endif

Is it safe to have vma with already freed vma_name? I suspect this is
safe because of mmap_lock but is there any reason to split the freeing
process and have this potential UAF lurking?

>  }
>  
>  static void account_kernel_stack(struct task_struct *tsk, int account)
> -- 
> 2.39.0

-- 
Michal Hocko
SUSE Labs