linux-kernel - Re: [PATCH 12/13] tracing/uprobes: Add more fetch functions

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Message-ID: <20131031182218.GB11208@redhat.com>
Date:	Thu, 31 Oct 2013 19:22:18 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Namhyung Kim <namhyung.kim@....com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Hyeoncheol Lee <cheol.lee@....com>,
	Hemant Kumar <hkshaw@...ux.vnet.ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	"zhangwei(Jovi)" <jovi.zhangwei@...wei.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
Subject: Re: [PATCH 12/13] tracing/uprobes: Add more fetch functions

On 10/29, Namhyung Kim wrote:
>
> +static void __user *get_user_vaddr(unsigned long addr, struct trace_uprobe *tu)
> +{
> +	unsigned long pgoff = addr >> PAGE_SHIFT;
> +	struct vm_area_struct *vma;
> +	struct address_space *mapping;
> +	unsigned long vaddr = 0;
> +
> +	if (tu == NULL) {
> +		/* A NULL tu means that we already got the vaddr */
> +		return (void __force __user *) addr;
> +	}
> +
> +	mapping = tu->inode->i_mapping;
> +
> +	mutex_lock(&mapping->i_mmap_mutex);
> +	vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
> +		if (vma->vm_mm != current->mm)
> +			continue;
> +		if (!(vma->vm_flags & VM_READ))
> +			continue;
> +
> +		vaddr = offset_to_vaddr(vma, addr);
> +		break;
> +	}
> +	mutex_unlock(&mapping->i_mmap_mutex);
> +
> +	WARN_ON_ONCE(vaddr == 0);

Hmm. But unless I missed something this "addr" passed as an argument can
be wrong? And if nothing else this or another thread can unmap the vma?

Oleg.

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