linux-kernel - Re: [PATCH v8 3/6] Uprobes: Support SDT markers having reference count (semaphore)

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Date:   Tue, 14 Aug 2018 14:26:49 +0530
From:   Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
To:     srikar@...ux.vnet.ibm.com, oleg@...hat.com, rostedt@...dmis.org,
        mhiramat@...nel.org, liu.song.a23@...il.com
Cc:     peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
        alexander.shishkin@...ux.intel.com, jolsa@...hat.com,
        namhyung@...nel.org, linux-kernel@...r.kernel.org,
        ananth@...ux.vnet.ibm.com, alexis.berlemont@...il.com,
        naveen.n.rao@...ux.vnet.ibm.com,
        linux-arm-kernel@...ts.infradead.org, linux-mips@...ux-mips.org,
        linux@...linux.org.uk, ralf@...ux-mips.org, paul.burton@...s.com,
        Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
Subject: Re: [PATCH v8 3/6] Uprobes: Support SDT markers having reference
 count (semaphore)


> +static int delayed_uprobe_install(struct vm_area_struct *vma)
> +{
> +	struct list_head *pos, *q;
> +	struct delayed_uprobe *du;
> +	unsigned long vaddr;
> +	int ret = 0, err = 0;
> +
> +	mutex_lock(&delayed_uprobe_lock);
> +	list_for_each_safe(pos, q, &delayed_uprobe_list) {
> +		du = list_entry(pos, struct delayed_uprobe, list);
> +
> +		if (!valid_ref_ctr_vma(du->uprobe, vma))
> +			continue;

I think we should compare mm here. I.e.:

    if (du->mm != vma->vm_mm || !valid_ref_ctr_vma(du->uprobe, vma))
            continue;

Otherwise things can mess up.

> +
> +		vaddr = offset_to_vaddr(vma, du->uprobe->ref_ctr_offset);
> +		ret = __update_ref_ctr(vma->vm_mm, vaddr, 1);
> +		/* Record an error and continue. */
> +		if (ret && !err)
> +			err = ret;
> +		delayed_uprobe_delete(du);
> +	}
> +	mutex_unlock(&delayed_uprobe_lock);
> +	return err;
> +}