Re: [PATCH 5/8] trace_uprobe: Support SDT markers having reference count (semaphore)

[Ravi Bangoria]

On 03/15/2018 08:00 PM, Oleg Nesterov wrote:
> On 03/15, Oleg Nesterov wrote:
>>> +static struct vm_area_struct *
>>> +sdt_find_vma(struct mm_struct *mm, struct trace_uprobe *tu)
>>> +{
>>> +	struct vm_area_struct *tmp;
>>> +
>>> +	for (tmp = mm->mmap; tmp != NULL; tmp = tmp->vm_next)
>>> +		if (sdt_valid_vma(tu, tmp))
>>> +			return tmp;
>>> +
>>> +	return NULL;
>> I can't understand the logic... Lets ignore sdt_valid_vma() for now.
>> The caller has uprobe_map_info, why it can't simply do
>> vma = find_vma(uprobe_map_info->vaddr)? and then check sdt_valid_vma().
> Note to mention that sdt_find_vma() can return NULL but the callers do
> vma_offset_to_vaddr(vma) without any check.

If the "mm" we are passing to sdt_find_vma() is returned by
uprobe_build_map_info(ref_ctr_offset), sdt_find_vma() must
_not_ return NULL.

Thanks for the review,
Ravi