[h323plus] Double-delete Capability bug

[Iurii Gordiienko]

I'm sure - current implementations ::AddCapability are wrong - we should't clone the pointer for  H323CodecExtendedVideoCapability :: AddCapability ( H323Capability * capability )  function and should clone for  H323CodecExtendedVideoCapability :: AddCapability ( const PString & cap ) function. I think, Valgrind shows memory leak for case when we are using  extCapabilities . Add ( H323ExtendedVideoFactory :: CreateInstance ( cap )->clone()) (forr H323CodecExtendedVideoCapability :: AddCapability ( const PString & cap ) )  because we have no any default mechanism to clear (delete all capabilities) capabilities factory - we have static factory objects as I remember and Valgrind don't see any desctructor execution. I will write (tomorrow ) simple app and show you proper behavior and destructors execution. We can't use current version (with clone()) of  H323CodecExtendedVideoCapability :: AddCapability ( H323Capability * capability ) fuction because that function has been declared as owner of pointer to H323Capability and any user expects that  H323CodecExtendedVideoCapability object will delete that pointer in own destructor. Whis current modiification we have 100% memory leak because it has not declared behaviour. 

2023 void H323CodecExtendedVideoCapability :: AddCapability ( const PString & cap ) 2024 { 2025 extCapabilities . Add ( H323ExtendedVideoFactory :: CreateInstance ( cap )); 2026 } 2027 2028 void H323CodecExtendedVideoCapability :: AddCapability ( H323Capability * capability ) 2029 { 2030 extCapabilities . Add (( H323Capability * ) capability -> Clone ()); 2031 } 

--- Original message --- 
From: "Simon Horne" <s.horne at packetizer.com> 
Date: 24 January 2016, 07:23:27 

Fix checked in. 
The first instance is created in
H323ExtendedVideoCapability::AddAllCapabilities and a new function
H323CodecExtendedVideoCapability::AddCapability(H323Capability *) then
clones the first instance. The first instance is then deleted. This will
ensure every subsequent call to H323ExtendedVideoFactory::CreateInstance()
will create a new unique instance and there is no memory leak.

Simon

-----Original Message-----
From: h323plus [mailto:h323plus-bounces at lists.packetizer.com] On Behalf Of
Jan Willamowius
Sent: Sunday, January 24, 2016 2:35 AM
To: h323plus at lists.packetizer.com 
Subject: Re: [h323plus] Double-delete Capability bug

Hi Simon,

it does need a better fix. But a leak is still better than a crash.

The proper fix is probably to have CreateInstance() always allocate new
memory. But until thats fixed I would leave the Clone() in.

Regards,
Jan

Simon Horne wrote:
> Jan
> 
> As I suspected, I just check with VLD on windows and the change causes 
> a 9kB/call memory leak (as the capability gets cloned 3 times per 
> call). Needs to be reverted out.
> 
> Simon
> 
> -----Original Message-----
> From: h323plus [mailto:h323plus-bounces at lists.packetizer.com] On 
> Behalf Of Jan Willamowius
> Sent: Saturday, January 23, 2016 4:49 AM
> To: h323plus at lists.packetizer.com 
> Subject: Re: [h323plus] Double-delete Capability bug
> 
> Hi Iurii,
> 
> I have added the Clone() in the CVS, but could you please check (wg.
> with Valgrind) if we now have a memory leak in some cases instead of a 
> crash ?
> 
> Regards,
> Jan
> 
> --
> Jan Willamowius, Founder of the GNU Gatekeeper Project EMail  :
> jan at willamowius.de 
> Website: http://www.gnugk.org 
> Support: http://www.willamowius.com/gnugk-support.html 
> 
> Relaxed Communications GmbH
> Frahmredder 91
> 22393 Hamburg
> Geschäftsführer: Jan Willamowius
> HRB 125261 (Amtsgericht Hamburg)
> USt-IdNr: DE286003584
> 
> Iurii Gordiienko wrote:
> > Hi,
> > I have found something... For
> H323ExtendedVideoCapability::AddAllCapabilities function we are using 
> H323CodecExtendedVideoCapability::AddCapability function for
> extCapability->AddCapability(*r).
> H323CodecExtendedVideoCapability::AddCapability function uses
> extCapabilities.Add(H323ExtendedVideoFactory::CreateInstance(cap))
function.
> The function H323ExtendedVideoFactory::CreateInstance(cap) will call "new"
> if any same "cap" does not is exists for now< for other case it will 
> return the pointer to current actual Capability. But 
> H323CodecExtendedVideoCapability::extCapabilities will delete all 
> items in time of execution  extCapabilities.RemoveAll() function from 
> H323CodecExtendedVideoCapability::~H323CodecExtendedVideoCapability().
> In result we have "double delete" and undefined behavior (crash for 
> worst case).
> > 
> > --------------------------------
> > void H323ExtendedVideoCapability::AddAllCapabilities(
> H323Capabilities & basecapabilities, PINDEX descriptorNum,PINDEX
> simultaneous) {   H323ExtendedVideoFactory::KeyList_T extCaps = 
> H323ExtendedVideoFactory::GetKeyList();   if (extCaps.size() > 0) { 
> H323CodecExtendedVideoCapability * capability = new 
> H323CodecExtendedVideoCapability();
> H323ExtendedVideoFactory::KeyList_T::const_iterator r;         PINDEX 
> num = P_MAX_INDEX;         for (r = extCaps.begin(); r != 
> extCaps.end(); ++r) {
>          H323CodecExtendedVideoCapability * extCapability = 
> (H323CodecExtendedVideoCapability *)capability->Clone();
>  extCapability->AddCapability(*r);            num = 
> basecapabilities.SetCapability(descriptorNum, 
> simultaneous,extCapability);
>          simultaneous = num;         }     simultaneous = P_MAX_INDEX; 
> basecapabilities.SetCapability(descriptorNum, simultaneous,new 
> H323ControlExtendedVideoCapability());  !
> >     delete capability;   }  }
> > void H323CodecExtendedVideoCapability::AddCapability(const PString &
> > cap) {
> > extCapabilities.Add(H323ExtendedVideoFactory::CreateInstance(cap)); 
> > }
> > 
> > -------------------------------------------------
> > I propose to replace the "void
> H323CodecExtendedVideoCapability::AddCapability(const PString & cap)" 
> to this one:
> > void H323CodecExtendedVideoCapability::AddCapability(const PString &
> > cap) {
> > extCapabilities.Add(H323ExtendedVideoFactory::CreateInstance(cap)->c
> > lo
> > ne()); }
> > 
> > 
> > 
> > Thanks -- Iurii Gordiienko


 
 
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