Re: [PATCH v5 3.1.0-rc4-tip 9/26] Uprobes: Background pagereplacement.

[Oleg Nesterov]

On 09/20, Srikar Dronamraju wrote:
>
> +int __weak read_opcode(struct task_struct *tsk, unsigned long vaddr,
> +						uprobe_opcode_t *opcode)
> +{
> +	struct vm_area_struct *vma;
> +	struct page *page;
> +	void *vaddr_new;
> +	int ret;
> +
> +	ret = get_user_pages(tsk, tsk->mm, vaddr, 1, 0, 0, &page, &vma);
> +	if (ret <= 0)
> +		return ret;
> +	ret = -EINVAL;
> +
> +	/*
> +	 * We are interested in text pages only. Our pages of interest
> +	 * should be mapped for read and execute only. We desist from
> +	 * adding probes in write mapped pages since the breakpoints
> +	 * might end up in the file copy.
> +	 */
> +	if (!valid_vma(vma))
> +		goto put_out;

Another case when valid_vma() looks suspicious. We are going to restore
the original instruction. We shouldn't fail (at least we shouldn't "leak"
->mm_uprobes_count) if ->vm_flags was changed between register_uprobe()
and unregister_uprobe().

Oleg.

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