linux-kernel - [PATCH v5 06/13] KVM: Move WARN on invalid memslot index to update

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Date:   Mon, 20 Sep 2021 23:38:54 +0200
From:   "Maciej S. Szmigiero" <mail@...iej.szmigiero.name>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Igor Mammedov <imammedo@...hat.com>,
        Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Huacai Chen <chenhuacai@...nel.org>,
        Aleksandar Markovic <aleksandar.qemu.devel@...il.com>,
        Paul Mackerras <paulus@...abs.org>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        David Hildenbrand <david@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v5 06/13] KVM: Move WARN on invalid memslot index to update_memslots()

From: "Maciej S. Szmigiero" <maciej.szmigiero@...cle.com>

Since kvm_memslot_move_forward() can theoretically return a negative
memslot index even when kvm_memslot_move_backward() returned a positive one
(and so did not WARN) let's just move the warning to the common code.

Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@...cle.com>
Reviewed-by: Claudio Imbrenda <imbrenda@...ux.ibm.com>
---
 virt/kvm/kvm_main.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 14043a6edb88..348fae880189 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1281,8 +1281,7 @@ static inline int kvm_memslot_move_backward(struct kvm_memslots *slots,
 	struct kvm_memory_slot *mslots = slots->memslots;
 	int i;
 
-	if (WARN_ON_ONCE(slots->id_to_index[memslot->id] == -1) ||
-	    WARN_ON_ONCE(!slots->used_slots))
+	if (slots->id_to_index[memslot->id] == -1 || !slots->used_slots)
 		return -1;
 
 	/*
@@ -1386,6 +1385,9 @@ static void update_memslots(struct kvm_memslots *slots,
 			i = kvm_memslot_move_backward(slots, memslot);
 		i = kvm_memslot_move_forward(slots, memslot, i);
 
+		if (WARN_ON_ONCE(i < 0))
+			return;
+
 		/*
 		 * Copy the memslot to its new position in memslots and update
 		 * its index accordingly.