Re: [PATCH] fork: avoid inappropriate uprobe access to invalid mm

[Oleg Nesterov]

I must have missed something, but...

On 12/10, Lorenzo Stoakes wrote:
>
> @@ -1746,9 +1741,11 @@ static struct mm_struct *dup_mm(struct task_struct *tsk,
>  	if (!mm_init(mm, tsk, mm->user_ns))
>  		goto fail_nomem;
> 
> +	uprobe_start_dup_mmap();
>  	err = dup_mmap(mm, oldmm);
>  	if (err)
> -		goto free_pt;
> +		goto free_pt_end_uprobe;
> +	uprobe_end_dup_mmap();
> 
>  	mm->hiwater_rss = get_mm_rss(mm);
>  	mm->hiwater_vm = mm->total_vm;
> @@ -1758,6 +1755,8 @@ static struct mm_struct *dup_mm(struct task_struct *tsk,
> 
>  	return mm;
> 
> +free_pt_end_uprobe:
> +	uprobe_end_dup_mmap();

if dup_mmap() fails and "mm" is incomplete, then with this version dup_mmap_sem
is dropped before __mmput/exit_mmap/etc. How can this help?

Oleg.