Re: [Xen-devel] [PATCH for-4.5 v2] libxc: don't leak buffer containing the uncompressed PV kernel

[Gedalya <gedalya@xxxxxxxxxxx>]

On 11/20/2014 10:13 PM, Gedalya wrote:
> On 11/20/2014 03:21 PM, Konrad Rzeszutek Wilk wrote:
> > On Thu, Nov 20, 2014 at 03:48:47PM +0000, Ian Campbell wrote:
> > > The libxc xc_dom_* infrastructure uses a very simple malloc memory 
> > > pool which
> > > is freed by xc_dom_release. However the various xc_try_*_decode 
> > > routines (other
> > > than the gzip one) just use plain malloc/realloc and therefore the 
> > > buffer ends
> > > up leaked.
> > >
> > > The memory pool currently supports mmap'd buffers as well as a directly
> > > allocated buffers, however the try decode routines make use of 
> > > realloc and do
> > > not fit well into this model. Introduce a concept of an external 
> > > memory block
> > > to the memory pool and provide an interface to register such memory.
> > >
> > > The mmap_ptr and mmap_len fields of the memblock tracking struct 
> > > lose their
> > > mmap_ prefix since they are now also used for external memory blocks.
> > >
> > > We are only seeing this now because the gzip decoder doesn't leak 
> > > and it's only
> > > relatively recently that kernels in the wild have switched to better
> > > compression.
> > >
> > > This is https://bugs.debian.org/767295
> > >
> > > Reported by: Gedalya <gedalya@xxxxxxxxxxx>
> > Gedelya,
> >
> > Could you also test this patch to make sure it does fix the
> > reported issue please?
> So here's what happens now.
> 1. Starts up tiny
> 2. reboot: leak
> 3. reboot: freed (process larger, but the delta is all/mostly shared 
> pages)
> 4. reboot: leak
> 5. reboot: freed
> etc..
For the record, I applied it again the xen package currently in debian, 
4.4.1-3, see attached patch.
The only problem was that tools/libxc/include/xc_dom.h is in 
tools/libxc/xc_dom.h, otherwise it applied fine.

Attachment: 0039-libxc-dont-leak-buffer-containing-the-uncompressed-pv-kernel
Description: Text document

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