Re: [Xen-devel] vfree crash

[Petre Ovidiu PIRCALABU <ppircalabu@xxxxxxxxxxxxxxx>]

On Mon, 2019-07-01 at 08:29 +0000, Paul Durrant wrote:
> > -----Original Message-----
> > From: Xen-devel <xen-devel-bounces@xxxxxxxxxxxxxxxxxxxx> On Behalf
> > Of Petre Ovidiu PIRCALABU
> > Sent: 28 June 2019 19:00
> > To: xen-devel@xxxxxxxxxxxxxxxxxxxx; Andrew Cooper <
> > Andrew.Cooper3@xxxxxxxxxx>
> > Cc: Alexandru Stefan ISAILA <aisaila@xxxxxxxxxxxxxxx>; 
> > rcojocaru@xxxxxxxxxxxxxxx
> > Subject: [Xen-devel] vfree crash
> > 
> > Hello,
> > 
> > I need your help to pinpoint the root cause of a problem. To my
> > understanding vfree should be used when allocating memory with
> > vmalloc.
> > 
> > But, I have the following scenario which results in a XEN crash:
> > - allocate a number of frames using vmalloc (vzalloc) (e.g. using a
> > domctl) and assign them to the calling domain
> > - map the frames using xenforeignmemory_map_resource
> 
> Do you really mean xenforeignmemory_map_resource()? If the memory is
> assigned to the calling domain then this is quite likely not to work.
> There were reference counting problems with that code, which is why
> caller assigned resources were dropped.
> 
>   Paul
> 

The problem lies with vfree because it creates a new list with the
pages, unmaps the va pointer and then frees the pages. If I do these
steps manually (without adding them to a new list) it works.

Many thanks,
Petre


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