Re: [Xen-devel] xc_map_foreign_bulk() memory leak in ARM version?

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Thu, 2013-05-16 at 19:36 +0400, Nyashka Surovski wrote:
> Hi Xen folks!
> 
> 
> I've faced with one strange thing in ARM version of Xen: when I use
> xc_map_foreign_bulk() to map some memory from domU to dom0, after
> unmap() for previous returned address - memory is not freed at all.
> 
> 
> Let's look at call stack:
> 
> 
> xc_map_foreign() -> 
>   linux_privcmd_map_foreign_bulk() -> 
>     { 
>     addr = mmap(fd); 
>     ioctl(fd, IOCTL_PRIVCMD_MMAPBATCH_V2 ); 
>     }  ->
>       alloc_empty_pages() ->
>         alloc_xenballoned_pages();
> 
> So, I think that unmap(addr) must call free_xenballoned_pages(), but
> this doesn't happen. =(
> Let me note, that mmap() knows about privcmd_close() function, and it
> is the place where free_xenballoned_pages() is called, So we have that
> unmap() doesn't call privcmd_close() at all. It's something strange
> for me.
> 
> Can somebody show me the place of my misunderstanding, or is it a real
> bug?

Do you mean munmap()?

I think munmap will eventually end up calling close, when the references
to the vma etc are gone. Since the code path is a bit twisty I'd be
tempted to throw in a debug printk to confirm though.

Can you share your usercode?

Ian.


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