linux-kernel - [PATCH 4.17 056/220] powerpc/64s/radix: Fix radix_kvm_prefetch_workaround paca access of not possible CPU

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Date:   Sun,  1 Jul 2018 18:21:20 +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, stable@...nel.org,
        Pridhiviraj Paidipeddi <ppaidipe@...ux.vnet.ibm.com>,
        Nicholas Piggin <npiggin@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: [PATCH 4.17 056/220] powerpc/64s/radix: Fix radix_kvm_prefetch_workaround paca access of not possible CPU

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

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

From: Nicholas Piggin <npiggin@...il.com>

commit 758380b8155f69b4e2f77f27562f8a7a466749d6 upstream.

If possible CPUs are limited (e.g., by kexec), then the kvm prefetch
workaround function can access the paca pointer for a !possible CPU.

Fixes: d2e60075a3d44 ("powerpc/64: Use array of paca pointers and allocate pacas individually")
Cc: stable@...nel.org
Reported-by: Pridhiviraj Paidipeddi <ppaidipe@...ux.vnet.ibm.com>
Tested-by: Pridhiviraj Paidipeddi <ppaidipe@...ux.vnet.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@...il.com>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/powerpc/mm/tlb-radix.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/arch/powerpc/mm/tlb-radix.c
+++ b/arch/powerpc/mm/tlb-radix.c
@@ -733,6 +733,8 @@ extern void radix_kvm_prefetch_workaroun
 		for (; sib <= cpu_last_thread_sibling(cpu) && !flush; sib++) {
 			if (sib == cpu)
 				continue;
+			if (!cpu_possible(sib))
+				continue;
 			if (paca_ptrs[sib]->kvm_hstate.kvm_vcpu)
 				flush = true;
 		}