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

[Oleg Nesterov]

On 03/16, Ravi Bangoria wrote:
>
> On 03/15/2018 08:00 PM, Oleg Nesterov wrote:
> > 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.

Not at all.

Once build_map_info() returns any mapping can go away. Otherwise, why do
you think the caller has to take ->mmap_sem and use find_vma()? If you
were right, build_map_info() could just return the list of vma's instead
of list of mm's.

Oleg.