Re: Memory leak in vmx.c

[Jan Kiszka <jan.kiszka@web.de>]

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On 2012-12-07 20:51, Andrew Honig wrote:
> I've noticed a memory leak that occurs in vmx.c.
> 
> In alloc_apic_access_page, it calls __kvm_set_memory_region(kvm,
> &kvm_userspace_mem, 0).  __kvm_set_memory_region calls
> kvm_arch_prepare_memory_region, which because the user_alloc parameter
> is 0 will allocate memory for the page with vm_mmap.
> 
> This memory never gets freed.   In kvm_arch_destroy_vm it calls
> put_page(kvm->arch.apic_access_page), but that only unpins the memory
> (necessary due to an earlier call to gfn_to_page), it never actually
> frees the memory.  The memory is allocated in the current process
> context so it's cleaned up when the process exits, but if a process
> creates and destroys multiple VMs then this leak starts to become a
> problem.
> 
> Similar leaks occur in alloc_identity_pagetable and vmx_set_tss_addr
> for a total of 5 pages of memory leak for a VM.  The vmx_set_tss_addr
> actually leaks each time vmx_set_tss_addr is called so this could also
> become a problem if a program had occasion to set the tss addr several
> times.

Both pages are per-vm. Therefore they are freed in kvm_arch_destroy_vm.
But I have to admit that I dug a while as well to find this out.

Jan


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