Re: [PATCH 1/1] mm: fix vma->anon_name memory leak for anonymous shmem VMAs

[David Hildenbrand]

On 03.01.23 20:53, Suren Baghdasaryan wrote:
> On Mon, Jan 2, 2023 at 4:00 AM David Hildenbrand <david@xxxxxxxxxx> wrote:
> > On 28.12.22 20:42, Suren Baghdasaryan wrote:
> > > free_anon_vma_name() is missing a check for anonymous shmem VMA which
> > > leads to a memory leak due to refcount not being dropped. Fix this by
> > > adding the missing check.
> > >
> > > Fixes: d09e8ca6cb93 ("mm: anonymous shared memory naming")
> > > Reported-by: syzbot+91edf9178386a07d06a7@xxxxxxxxxxxxxxxxxxxxxxxxx
> > > Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
> > > ---
> > >    include/linux/mm_inline.h | 2 +-
> > >    1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h
> > > index e8ed225d8f7c..d650ca2c5d29 100644
> > > --- a/include/linux/mm_inline.h
> > > +++ b/include/linux/mm_inline.h
> > > @@ -413,7 +413,7 @@ static inline void free_anon_vma_name(struct vm_area_struct *vma)
> > >         * Not using anon_vma_name because it generates a warning if mmap_lock
> > >         * is not held, which might be the case here.
> > >         */
> > > -     if (!vma->vm_file)
> > > +     if (!vma->vm_file || vma_is_anon_shmem(vma))
> > >                anon_vma_name_put(vma->anon_name);
> >
> > Wouldn't it be me more consistent to check for "vma->anon_name"?
> >
> > That's what dup_anon_vma_name() checks. And it's safe now because
> > anon_name is no longer overloaded in vm_area_struct.
>
> Thanks for the suggestion, David. Yes, with the recent change that
> does not overload anon_name, checking for "vma->anon_name" would be
> simpler. I think we can also drop anon_vma_name() function now
> (https://elixir.bootlin.com/linux/v6.2-rc2/source/mm/madvise.c#L94)
> since vma->anon_name does not depend on vma->vm_file anymore, remove
> the last part of this comment:
> https://elixir.bootlin.com/linux/v6.2-rc2/source/include/linux/mm_types.h#L584
> and use vma->anon_name directly going forward. If all that sounds
> good, I'll post a separate patch implementing all these changes.
> So, for this patch I would suggest keeping it as is because
> functionally it is correct and will change this check along with other
> corrections I mentioned above in a separate patch. Does that sound
> good?

Works for me.

Acked-by: David Hildenbrand <david@xxxxxxxxxx>

for this one, as it fixes the issue.

--
Thanks,

David / dhildenb