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

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

[Suren Baghdasaryan]

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@syzkaller.appspotmail.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
---
 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);
 }
 
-- 
2.39.0.314.g84b9a713c41-goog

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

[David Hildenbrand]

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@syzkaller.appspotmail.com
> Signed-off-by: Suren Baghdasaryan <surenb@google.com>
> ---
>   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,

David / dhildenb

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

[Suren Baghdasaryan]

On Mon, Jan 2, 2023 at 4:00 AM David Hildenbrand <david@redhat.com> 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@syzkaller.appspotmail.com
> > Signed-off-by: Suren Baghdasaryan <surenb@google.com>
> > ---
> >   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?


-     if (!vma->vm_file)
+     if (!vma->vm_file || vma_is_anon_shmem(vma))

>
> --
> Thanks,
>
> David / dhildenb
>

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@redhat.com> 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@syzkaller.appspotmail.com
>>> Signed-off-by: Suren Baghdasaryan <surenb@google.com>
>>> ---
>>>    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@redhat.com>

for this one, as it fixes the issue.

-- 
Thanks,

David / dhildenb

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

[Suren Baghdasaryan]

On Wed, Jan 4, 2023 at 1:04 AM David Hildenbrand <david@redhat.com> wrote:
>
> On 03.01.23 20:53, Suren Baghdasaryan wrote:
> > On Mon, Jan 2, 2023 at 4:00 AM David Hildenbrand <david@redhat.com> 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@syzkaller.appspotmail.com
> >>> Signed-off-by: Suren Baghdasaryan <surenb@google.com>
> >>> ---
> >>>    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@redhat.com>

Thank you! Will post the followup cleanup patch shorly.

>
> for this one, as it fixes the issue.
>
> --
> Thanks,
>
> David / dhildenb
>

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

[Suren Baghdasaryan]

On Wed, Jan 4, 2023 at 10:24 AM Suren Baghdasaryan <surenb@google.com> wrote:
>
> On Wed, Jan 4, 2023 at 1:04 AM David Hildenbrand <david@redhat.com> wrote:
> >
> > On 03.01.23 20:53, Suren Baghdasaryan wrote:
> > > On Mon, Jan 2, 2023 at 4:00 AM David Hildenbrand <david@redhat.com> 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@syzkaller.appspotmail.com
> > >>> Signed-off-by: Suren Baghdasaryan <surenb@google.com>
> > >>> ---
> > >>>    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@redhat.com>
>
> Thank you! Will post the followup cleanup patch shorly.

Andrew, I posted v2 of this patch at
https://lore.kernel.org/all/20230105000241.1450843-1-surenb@google.com/.
Please replace the original one in your tree. I had to follow David's
original suggestion instead of my planned cleanup because removing
anon_vma_name() would require us to add #ifdef CONFIG_ANON_VMA_NAME
everywhere we use vma->anon_name, which is quite ugly.
Thanks,
Suren.

>
> >
> > for this one, as it fixes the issue.
> >
> > --
> > Thanks,
> >
> > David / dhildenb
> >