From b42fc3cbc3d6e284463e93896679379443e19d56 Mon Sep 17 00:00:00 2001 From: Jeff Mahoney Date: Tue, 12 Apr 2011 21:30:17 -0400 Subject: [PATCH] KVM: Fix off by one in kvm_for_each_vcpu iteration This patch avoids gcc issuing the following warning when KVM_MAX_VCPUS=1: warning: array subscript is above array bounds kvm_for_each_vcpu currently checks to see if the index for the vcpu is valid /after/ loading it. We don't run into problems because the address is still inside the enclosing struct kvm and we never deference or write to it, so this isn't a security issue. The warning occurs when KVM_MAX_VCPUS=1 because the increment portion of the loop will *always* cause the loop to load an invalid location since ++idx will always be > 0. This patch moves the load so that the check occurs before the load and we don't run into the compiler warning. Signed-off-by: Neil Brown Signed-off-by: Jeff Mahoney Signed-off-by: Avi Kivity --- include/linux/kvm_host.h | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index d1f5075..0bc3d37 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -296,9 +296,10 @@ static inline struct kvm_vcpu *kvm_get_vcpu(struct kvm *kvm, int i) } #define kvm_for_each_vcpu(idx, vcpup, kvm) \ - for (idx = 0, vcpup = kvm_get_vcpu(kvm, idx); \ - idx < atomic_read(&kvm->online_vcpus) && vcpup; \ - vcpup = kvm_get_vcpu(kvm, ++idx)) + for (idx = 0; \ + idx < atomic_read(&kvm->online_vcpus) && \ + (vcpup = kvm_get_vcpu(kvm, idx)) != NULL; \ + idx++) int kvm_vcpu_init(struct kvm_vcpu *vcpu, struct kvm *kvm, unsigned id); void kvm_vcpu_uninit(struct kvm_vcpu *vcpu); -- 2.7.4