linux-kernel - [PATCH 4.13 020/110] KVM: PPC: Book3S HV: Hold kvm->lock around call to kvmppc_update

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Date:   Tue,  3 Oct 2017 14:28:42 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Paul Mackerras <paulus@...abs.org>
Subject: [PATCH 4.13 020/110] KVM: PPC: Book3S HV: Hold kvm->lock around call to kvmppc_update_lpcr

4.13-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Paul Mackerras <paulus@...abs.org>

commit cf5f6f3125241853462334b1bc696f3c3c492178 upstream.

Commit 468808bd35c4 ("KVM: PPC: Book3S HV: Set process table for HPT
guests on POWER9", 2017-01-30) added a call to kvmppc_update_lpcr()
which doesn't hold the kvm->lock mutex around the call, as required.
This adds the lock/unlock pair, and for good measure, includes
the kvmppc_setup_partition_table() call in the locked region, since
it is altering global state of the VM.

This error appears not to have any fatal consequences for the host;
the consequences would be that the VCPUs could end up running with
different LPCR values, or an update to the LPCR value by userspace
using the one_reg interface could get overwritten, or the update
done by kvmhv_configure_mmu() could get overwritten.

Fixes: 468808bd35c4 ("KVM: PPC: Book3S HV: Set process table for HPT guests on POWER9")
Signed-off-by: Paul Mackerras <paulus@...abs.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/powerpc/kvm/book3s_hv.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -4187,11 +4187,13 @@ static int kvmhv_configure_mmu(struct kv
 	if ((cfg->process_table & PRTS_MASK) > 24)
 		return -EINVAL;

+	mutex_lock(&kvm->lock);
 	kvm->arch.process_table = cfg->process_table;
 	kvmppc_setup_partition_table(kvm);

 	lpcr = (cfg->flags & KVM_PPC_MMUV3_GTSE) ? LPCR_GTSE : 0;
 	kvmppc_update_lpcr(kvm, lpcr, LPCR_GTSE);
+	mutex_unlock(&kvm->lock);

 	return 0;
 }