[PATCH][next] KVM: x86/mmu: Fix uninitialized boolean variable flush

[PATCH][next] KVM: x86/mmu: Fix uninitialized boolean variable flush

[Colin King]

From: Colin Ian King <colin.king@canonical.com>

In the case where kvm_memslots_have_rmaps(kvm) is false the boolean
variable flush is not set and is uninitialized.  If is_tdp_mmu_enabled(kvm)
is true then the call to kvm_tdp_mmu_zap_collapsible_sptes passes the
uninitialized value of flush into the call. Fix this by initializing
flush to false.

Addresses-Coverity: ("Uninitialized scalar variable")
Fixes: e2209710ccc5 ("KVM: x86/mmu: Skip rmap operations if rmaps not allocated")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 arch/x86/kvm/mmu/mmu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index ed24e97c1549..b8d20f139729 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -5689,7 +5689,7 @@ void kvm_mmu_zap_collapsible_sptes(struct kvm *kvm,
 {
 	/* FIXME: const-ify all uses of struct kvm_memory_slot.  */
 	struct kvm_memory_slot *slot = (struct kvm_memory_slot *)memslot;
-	bool flush;
+	bool flush = false;
 
 	if (kvm_memslots_have_rmaps(kvm)) {
 		write_lock(&kvm->mmu_lock);
-- 
2.31.1

Re: [PATCH][next] KVM: x86/mmu: Fix uninitialized boolean variable flush

[Sean Christopherson]

On Tue, Jun 22, 2021, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
> 
> In the case where kvm_memslots_have_rmaps(kvm) is false the boolean
> variable flush is not set and is uninitialized.  If is_tdp_mmu_enabled(kvm)
> is true then the call to kvm_tdp_mmu_zap_collapsible_sptes passes the
> uninitialized value of flush into the call. Fix this by initializing
> flush to false.
> 
> Addresses-Coverity: ("Uninitialized scalar variable")
> Fixes: e2209710ccc5 ("KVM: x86/mmu: Skip rmap operations if rmaps not allocated")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> ---

Reviewed-by: Sean Christopherson <seanjc@google.com>

Re: [PATCH][next] KVM: x86/mmu: Fix uninitialized boolean variable flush

[Paolo Bonzini]

On 22/06/21 17:09, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
> 
> In the case where kvm_memslots_have_rmaps(kvm) is false the boolean
> variable flush is not set and is uninitialized.  If is_tdp_mmu_enabled(kvm)
> is true then the call to kvm_tdp_mmu_zap_collapsible_sptes passes the
> uninitialized value of flush into the call. Fix this by initializing
> flush to false.
> 
> Addresses-Coverity: ("Uninitialized scalar variable")
> Fixes: e2209710ccc5 ("KVM: x86/mmu: Skip rmap operations if rmaps not allocated")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> ---
>   arch/x86/kvm/mmu/mmu.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index ed24e97c1549..b8d20f139729 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -5689,7 +5689,7 @@ void kvm_mmu_zap_collapsible_sptes(struct kvm *kvm,
>   {
>   	/* FIXME: const-ify all uses of struct kvm_memory_slot.  */
>   	struct kvm_memory_slot *slot = (struct kvm_memory_slot *)memslot;
> -	bool flush;
> +	bool flush = false;
>   
>   	if (kvm_memslots_have_rmaps(kvm)) {
>   		write_lock(&kvm->mmu_lock);
> 

Queued, thanks.

Paolo