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SubjectRe: [PATCH 2/2] KVM: arm64: vgic-its: Fix memory leak on the error path of vgic_add_lpi()
On 2020-04-16 02:17, Zenghui Yu wrote:
> On 2020/4/14 11:03, Zenghui Yu wrote:
>> If we're going to fail out the vgic_add_lpi(), let's make sure the
>> allocated vgic_irq memory is also freed. Though it seems that both
>> cases are unlikely to fail.
>>
>> Cc: Zengruan Ye <yezengruan@huawei.com>
>> Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
>> ---
>> virt/kvm/arm/vgic/vgic-its.c | 8 ++++++--
>> 1 file changed, 6 insertions(+), 2 deletions(-)
>>
>> diff --git a/virt/kvm/arm/vgic/vgic-its.c
>> b/virt/kvm/arm/vgic/vgic-its.c
>> index d53d34a33e35..3c3b6a0f2dce 100644
>> --- a/virt/kvm/arm/vgic/vgic-its.c
>> +++ b/virt/kvm/arm/vgic/vgic-its.c
>> @@ -98,12 +98,16 @@ static struct vgic_irq *vgic_add_lpi(struct kvm
>> *kvm, u32 intid,
>> * the respective config data from memory here upon mapping the
>> LPI.
>> */
>> ret = update_lpi_config(kvm, irq, NULL, false);
>> - if (ret)
>> + if (ret) {
>> + kfree(irq);
>> return ERR_PTR(ret);
>> + }
>> ret = vgic_v3_lpi_sync_pending_status(kvm, irq);
>> - if (ret)
>> + if (ret) {
>> + kfree(irq);
>> return ERR_PTR(ret);
>> + }
>
> Looking at it again, I realized that this error handling is still not
> complete. Maybe we should use a vgic_put_irq() instead so that we can
> also properly delete the vgic_irq from lpi_list.

Yes, this is a more correct fix indeed. There is still a bit of a
bizarre
behaviour if you have two vgic_add_lpi() racing to create the same
interrupt,
which is pretty dodgy anyway (it means we have two MAPI at the same
time...).
You end-up with re-reading the state from memory... Oh well.

> Marc, what do you think? Could you please help to fix it, or I can
> resend it.

I've fixed it as such (with a comment for a good measure):

diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
index 3c3b6a0f2dce..c012a52b19f5 100644
--- a/virt/kvm/arm/vgic/vgic-its.c
+++ b/virt/kvm/arm/vgic/vgic-its.c
@@ -96,16 +96,19 @@ static struct vgic_irq *vgic_add_lpi(struct kvm
*kvm, u32 intid,
* We "cache" the configuration table entries in our struct
vgic_irq's.
* However we only have those structs for mapped IRQs, so we read in
* the respective config data from memory here upon mapping the LPI.
+ *
+ * Should any of these fail, behave as if we couldn't create the LPI
+ * by dropping the refcount and returning the error.
*/
ret = update_lpi_config(kvm, irq, NULL, false);
if (ret) {
- kfree(irq);
+ vgic_put_irq(kvm, irq);
return ERR_PTR(ret);
}

ret = vgic_v3_lpi_sync_pending_status(kvm, irq);
if (ret) {
- kfree(irq);
+ vgic_put_irq(kvm, irq);
return ERR_PTR(ret);
}

Let me know if you agree with that.

Thanks,

M.
--
Jazz is not dead. It just smells funny...

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