[B.A.T.M.A.N.] [PATCH-maint] batman-adv: fix potential orig_node reference leak

[B.A.T.M.A.N.] [PATCH-maint] batman-adv: fix potential orig_node reference leak

[Simon Wunderlich]

Since batadv_orig_node_new() sets the refcount to two, assuming that
the calling function will use a reference for putting the orig_node into
a hash or similar, both references must be freed if initialization of
the orig_node fails. Otherwise that object may be leaked in that error
case.

Reported-by: Antonio Quartulli <antonio@meshcoding.com>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
---
 bat_iv_ogm.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/bat_iv_ogm.c b/bat_iv_ogm.c
index 6f4fcdc..6000337 100644
--- a/bat_iv_ogm.c
+++ b/bat_iv_ogm.c
@@ -256,6 +256,8 @@ batadv_iv_ogm_orig_get(struct batadv_priv *bat_priv, const uint8_t *addr)
 free_bcast_own:
 	kfree(orig_node->bat_iv.bcast_own);
 free_orig_node:
+	/* free twice, as batadv_orig_node_new set refcount to 2 */
+	batadv_orig_node_free_ref(orig_node);
 	batadv_orig_node_free_ref(orig_node);
 
 	return NULL;
-- 
1.7.10.4

Re: [B.A.T.M.A.N.] [PATCH-maint] batman-adv: fix potential orig_node reference leak

[Marek Lindner]

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On Saturday 08 February 2014 16:45:06 Simon Wunderlich wrote:
> Since batadv_orig_node_new() sets the refcount to two, assuming that
> the calling function will use a reference for putting the orig_node into
> a hash or similar, both references must be freed if initialization of
> the orig_node fails. Otherwise that object may be leaked in that error
> case.
> 
> Reported-by: Antonio Quartulli <antonio@meshcoding.com>
> Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
> ---
>  bat_iv_ogm.c |    2 ++
>  1 file changed, 2 insertions(+)

Applied in revision cb4d66e.

Thanks,
Marek

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Re: [B.A.T.M.A.N.] [PATCH-maint] batman-adv: fix potential orig_node reference leak

[Antonio Quartulli]

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On 08/02/14 16:45, Simon Wunderlich wrote:
> Since batadv_orig_node_new() sets the refcount to two, assuming that
> the calling function will use a reference for putting the orig_node into
> a hash or similar, both references must be freed if initialization of
> the orig_node fails. Otherwise that object may be leaked in that error
> case.
> 
> Reported-by: Antonio Quartulli <antonio@meshcoding.com>
> Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
> ---
>  bat_iv_ogm.c |    2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/bat_iv_ogm.c b/bat_iv_ogm.c
> index 6f4fcdc..6000337 100644
> --- a/bat_iv_ogm.c
> +++ b/bat_iv_ogm.c
> @@ -256,6 +256,8 @@ batadv_iv_ogm_orig_get(struct batadv_priv *bat_priv, const uint8_t *addr)
>  free_bcast_own:
>  	kfree(orig_node->bat_iv.bcast_own);
>  free_orig_node:
> +	/* free twice, as batadv_orig_node_new set refcount to 2 */
> +	batadv_orig_node_free_ref(orig_node);
>  	batadv_orig_node_free_ref(orig_node);

Coudln't we just invoke kfree(orig_node) here ? I think that if we hit
this point it is because the node has not added to the hash and
therefore it i snot used in any other context. This way we avoid the
double free_ref() and we don't trgger the whole RCU mechanism.

Or am I missing something?

Cheers,

-- 
Antonio Quartulli


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Re: [B.A.T.M.A.N.] [PATCH-maint] batman-adv: fix potential orig_node reference leak

[Martin Hundebøll]

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On 2014-02-11 18:26, Antonio Quartulli wrote:
> On 08/02/14 16:45, Simon Wunderlich wrote:
>> Since batadv_orig_node_new() sets the refcount to two, assuming that
>> the calling function will use a reference for putting the orig_node into
>> a hash or similar, both references must be freed if initialization of
>> the orig_node fails. Otherwise that object may be leaked in that error
>> case.
>>
>> Reported-by: Antonio Quartulli <antonio@meshcoding.com>
>> Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
>> ---
>>  bat_iv_ogm.c |    2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/bat_iv_ogm.c b/bat_iv_ogm.c
>> index 6f4fcdc..6000337 100644
>> --- a/bat_iv_ogm.c
>> +++ b/bat_iv_ogm.c
>> @@ -256,6 +256,8 @@ batadv_iv_ogm_orig_get(struct batadv_priv *bat_priv, const uint8_t *addr)
>>  free_bcast_own:
>>  	kfree(orig_node->bat_iv.bcast_own);
>>  free_orig_node:
>> +	/* free twice, as batadv_orig_node_new set refcount to 2 */
>> +	batadv_orig_node_free_ref(orig_node);
>>  	batadv_orig_node_free_ref(orig_node);
> 
> Coudln't we just invoke kfree(orig_node) here ? I think that if we hit
> this point it is because the node has not added to the hash and
> therefore it i snot used in any other context. This way we avoid the
> double free_ref() and we don't trgger the whole RCU mechanism.
> 
> Or am I missing something?

batadv_<type>_free_ref() might have side effect that are not handled by
kfree alone...

-- 
Kind Regards
Martin Hundebøll
Frederiks Allé 99, 1.th
8000 Aarhus C
Denmark

+45 61 65 54 61
martin@hundeboll.net


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Re: [B.A.T.M.A.N.] [PATCH-maint] batman-adv: fix potential orig_node reference leak

[Antonio Quartulli]

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On 11/02/14 18:29, Martin Hundebøll wrote:
> On 2014-02-11 18:26, Antonio Quartulli wrote:
>> On 08/02/14 16:45, Simon Wunderlich wrote:
>>> Since batadv_orig_node_new() sets the refcount to two, assuming that
>>> the calling function will use a reference for putting the orig_node into
>>> a hash or similar, both references must be freed if initialization of
>>> the orig_node fails. Otherwise that object may be leaked in that error
>>> case.
>>>
>>> Reported-by: Antonio Quartulli <antonio@meshcoding.com>
>>> Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
>>> ---
>>>  bat_iv_ogm.c |    2 ++
>>>  1 file changed, 2 insertions(+)
>>>
>>> diff --git a/bat_iv_ogm.c b/bat_iv_ogm.c
>>> index 6f4fcdc..6000337 100644
>>> --- a/bat_iv_ogm.c
>>> +++ b/bat_iv_ogm.c
>>> @@ -256,6 +256,8 @@ batadv_iv_ogm_orig_get(struct batadv_priv *bat_priv, const uint8_t *addr)
>>>  free_bcast_own:
>>>  	kfree(orig_node->bat_iv.bcast_own);
>>>  free_orig_node:
>>> +	/* free twice, as batadv_orig_node_new set refcount to 2 */
>>> +	batadv_orig_node_free_ref(orig_node);
>>>  	batadv_orig_node_free_ref(orig_node);
>>
>> Coudln't we just invoke kfree(orig_node) here ? I think that if we hit
>> this point it is because the node has not added to the hash and
>> therefore it i snot used in any other context. This way we avoid the
>> double free_ref() and we don't trgger the whole RCU mechanism.
>>
>> Or am I missing something?
> 
> batadv_<type>_free_ref() might have side effect that are not handled by
> kfree alone...

true, but since the orig_node has not been returned yet there is no
other component in batman-adv which is using it.

Otherwise, we may want to define and invoke a free_now() version of this
function (like we have done for other objects). But I think kfree() is
safe here.


Cheers,



-- 
Antonio Quartulli


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Re: [B.A.T.M.A.N.] [PATCH-maint] batman-adv: fix potential orig_node reference leak

[Simon Wunderlich]

> On 08/02/14 16:45, Simon Wunderlich wrote:
> > Since batadv_orig_node_new() sets the refcount to two, assuming that
> > the calling function will use a reference for putting the orig_node into
> > a hash or similar, both references must be freed if initialization of
> > the orig_node fails. Otherwise that object may be leaked in that error
> > case.
> > 
> > Reported-by: Antonio Quartulli <antonio@meshcoding.com>
> > Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
> > ---
> > 
> >  bat_iv_ogm.c |    2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/bat_iv_ogm.c b/bat_iv_ogm.c
> > index 6f4fcdc..6000337 100644
> > --- a/bat_iv_ogm.c
> > +++ b/bat_iv_ogm.c
> > @@ -256,6 +256,8 @@ batadv_iv_ogm_orig_get(struct batadv_priv *bat_priv,
> > const uint8_t *addr)
> > 
> >  free_bcast_own:
> >  	kfree(orig_node->bat_iv.bcast_own);
> >  
> >  free_orig_node:
> > +	/* free twice, as batadv_orig_node_new set refcount to 2 */
> > +	batadv_orig_node_free_ref(orig_node);
> > 
> >  	batadv_orig_node_free_ref(orig_node);
> 
> Coudln't we just invoke kfree(orig_node) here ? I think that if we hit
> this point it is because the node has not added to the hash and
> therefore it i snot used in any other context. This way we avoid the
> double free_ref() and we don't trgger the whole RCU mechanism.
> 
> Or am I missing something?

What about already allocated substructures like bat_iv.bcast_own, 
bat_iv.bacst_own_sum etc? Of course we could find out which is already 
allocated and free that too, but that orig node free function does already 
that.

Cheers,
    Simon

Re: [B.A.T.M.A.N.] [PATCH-maint] batman-adv: fix potential orig_node reference leak

[Marek Lindner]

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On Tuesday 11 February 2014 18:34:10 Antonio Quartulli wrote:
> true, but since the orig_node has not been returned yet there is no
> other component in batman-adv which is using it.
> 
> Otherwise, we may want to define and invoke a free_now() version of this
> function (like we have done for other objects). But I think kfree() is
> safe here.

It may be safe now but will surely be forgotten later. A guaranteed source for 
trouble. That is why we have cleanup routines for everything.

Cheers,
Marek

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Re: [B.A.T.M.A.N.] [PATCH-maint] batman-adv: fix potential orig_node reference leak

[Antonio Quartulli]

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On 11/02/14 18:40, Marek Lindner wrote:
> On Tuesday 11 February 2014 18:34:10 Antonio Quartulli wrote:
>> true, but since the orig_node has not been returned yet there is no
>> other component in batman-adv which is using it.
>>
>> Otherwise, we may want to define and invoke a free_now() version of this
>> function (like we have done for other objects). But I think kfree() is
>> safe here.
> 
> It may be safe now but will surely be forgotten later. A guaranteed source for 
> trouble. That is why we have cleanup routines for everything.
> 

True, in particular because we (as bat_iv_ogm.c) do not know what
batadv_orig_node_new() has allocated - a kfree() would be fine if the
object was allocated with a plain kmalloc(), but this is not the case.

By the way we have a bug here:
if we jump to

 256 free_bcast_own:
 257         kfree(orig_node->bat_iv.bcast_own);

bcast_own gets free'd but not assigned to NULL. Later
batadv_orig_node_free_rcu() (scheduled by batadv_orig_node_free_ref())
will call batadv_iv_ogm_orig_free() that will try to kfree() bcast_own
again (line 98 in bat_iv_ogm.c), thus leading to a double free. no?


Cheers,


-- 
Antonio Quartulli


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