Re: [PATCH] KVM: x86/mmu: fix NULL pointer dereference on guest INVPCID

[Greg KH <gregkh@linuxfoundation.org>]

On Tue, May 24, 2022 at 05:11:18PM +0200, Vegard Nossum wrote:
> From: Paolo Bonzini <pbonzini@redhat.com>
> 
> commit 9f46c187e2e680ecd9de7983e4d081c3391acc76 upstream.
> 
> With shadow paging enabled, the INVPCID instruction results in a call
> to kvm_mmu_invpcid_gva.  If INVPCID is executed with CR0.PG=0, the
> invlpg callback is not set and the result is a NULL pointer dereference.
> Fix it trivially by checking for mmu->invlpg before every call.
> 
> There are other possibilities:
> 
> - check for CR0.PG, because KVM (like all Intel processors after P5)
>   flushes guest TLB on CR0.PG changes so that INVPCID/INVLPG are a
>   nop with paging disabled
> 
> - check for EFER.LMA, because KVM syncs and flushes when switching
>   MMU contexts outside of 64-bit mode
> 
> All of these are tricky, go for the simple solution.  This is CVE-2022-1789.
> 
> Reported-by: Yongkang Jia <kangel@zju.edu.cn>
> Cc: stable@vger.kernel.org
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> [fix conflict due to missing b9e5603c2a3accbadfec570ac501a54431a6bdba]
> Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
> ---
>  arch/x86/kvm/mmu/mmu.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)

What kernel tree(s) are you wanting this to be applied to?

thanks,

greg k-h