[PATCH][next] KVM: x86: Fix potential fput on a null source_kvm_file

[PATCH][next] KVM: x86: Fix potential fput on a null source_kvm_file

[Colin King]

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

The fget can potentially return null, so the fput on the error return
path can cause a null pointer dereference. Fix this by checking for
a null source_kvm_file before doing a fput.

Addresses-Coverity: ("Dereference null return")
Fixes: 54526d1fd593 ("KVM: x86: Support KVM VMs sharing SEV context")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 arch/x86/kvm/svm/sev.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 1356ee095cd5..8b11c711a0e4 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -1764,7 +1764,8 @@ int svm_vm_copy_asid_from(struct kvm *kvm, unsigned int source_fd)
 e_source_unlock:
 	mutex_unlock(&source_kvm->lock);
 e_source_put:
-	fput(source_kvm_file);
+	if (source_kvm_file)
+		fput(source_kvm_file);
 	return ret;
 }
 
-- 
2.30.2

Re: [PATCH][next] KVM: x86: Fix potential fput on a null source_kvm_file

[Paolo Bonzini]

On 30/04/21 19:03, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
> 
> The fget can potentially return null, so the fput on the error return
> path can cause a null pointer dereference. Fix this by checking for
> a null source_kvm_file before doing a fput.
> 
> Addresses-Coverity: ("Dereference null return")
> Fixes: 54526d1fd593 ("KVM: x86: Support KVM VMs sharing SEV context")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> ---
>   arch/x86/kvm/svm/sev.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 1356ee095cd5..8b11c711a0e4 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -1764,7 +1764,8 @@ int svm_vm_copy_asid_from(struct kvm *kvm, unsigned int source_fd)
>   e_source_unlock:
>   	mutex_unlock(&source_kvm->lock);
>   e_source_put:
> -	fput(source_kvm_file);
> +	if (source_kvm_file)
> +		fput(source_kvm_file);
>   	return ret;
>   }
>   
> 

Queued, thanks.

Paolo