[PATCH 0/2] KVM: arm64: vgic_irq: Fix memory leaks

[PATCH 0/2] KVM: arm64: vgic_irq: Fix memory leaks

[Zenghui Yu]

A memory leak on vgic_irq structure was recently reported by kmemleak
on the guest destroy (or shutdown). It turned out that there're still
pending interrupts (LPI) staying in the vcpu's ap_list during destroy
so that KVM can't free the vgic_irq structure due to an extra refcount.

Patch #1 is intended to fix this issue. Patch #2 is a memory leak fix
on the error path, noticed while debugging.

Zenghui Yu (2):
  KVM: arm64: vgic-v3: Retire all pending LPIs on vcpu destroy
  KVM: arm64: vgic-its: Fix memory leak on the error path of
    vgic_add_lpi()

 virt/kvm/arm/vgic/vgic-init.c | 6 ++++++
 virt/kvm/arm/vgic/vgic-its.c  | 8 ++++++--
 2 files changed, 12 insertions(+), 2 deletions(-)

-- 
2.19.1



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[PATCH 1/2] KVM: arm64: vgic-v3: Retire all pending LPIs on vcpu destroy

[Zenghui Yu]

It's likely that the vcpu fails to handle all virtual interrupts if
userspace decides to destroy it, leaving the pending ones stay in the
ap_list. If the un-handled one is a LPI, its vgic_irq structure will
be eventually leaked because of an extra refcount increment in
vgic_queue_irq_unlock().

This was detected by kmemleak on almost every guest destroy, the
backtrace is as follows:

unreferenced object 0xffff80725aed5500 (size 128):
comm "CPU 5/KVM", pid 40711, jiffies 4298024754 (age 166366.512s)
hex dump (first 32 bytes):
00 00 00 00 00 00 00 00 08 01 a9 73 6d 80 ff ff ...........sm...
c8 61 ee a9 00 20 ff ff 28 1e 55 81 6c 80 ff ff .a... ..(.U.l...
backtrace:
[<000000004bcaa122>] kmem_cache_alloc_trace+0x2dc/0x418
[<0000000069c7dabb>] vgic_add_lpi+0x88/0x418
[<00000000bfefd5c5>] vgic_its_cmd_handle_mapi+0x4dc/0x588
[<00000000cf993975>] vgic_its_process_commands.part.5+0x484/0x1198
[<000000004bd3f8e3>] vgic_its_process_commands+0x50/0x80
[<00000000b9a65b2b>] vgic_mmio_write_its_cwriter+0xac/0x108
[<0000000009641ebb>] dispatch_mmio_write+0xd0/0x188
[<000000008f79d288>] __kvm_io_bus_write+0x134/0x240
[<00000000882f39ac>] kvm_io_bus_write+0xe0/0x150
[<0000000078197602>] io_mem_abort+0x484/0x7b8
[<0000000060954e3c>] kvm_handle_guest_abort+0x4cc/0xa58
[<00000000e0d0cd65>] handle_exit+0x24c/0x770
[<00000000b44a7fad>] kvm_arch_vcpu_ioctl_run+0x460/0x1988
[<0000000025fb897c>] kvm_vcpu_ioctl+0x4f8/0xee0
[<000000003271e317>] do_vfs_ioctl+0x160/0xcd8
[<00000000e7f39607>] ksys_ioctl+0x98/0xd8

Fix it by retiring all pending LPIs in the ap_list on the destroy path.

p.s. I can also reproduce it on a normal guest shutdown. It is because
userspace still send LPIs to vcpu (through KVM_SIGNAL_MSI ioctl) while
the guest is being shutdown and unable to handle it. A little strange
though and haven't dig further...

Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
---
 virt/kvm/arm/vgic/vgic-init.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/virt/kvm/arm/vgic/vgic-init.c b/virt/kvm/arm/vgic/vgic-init.c
index a963b9d766b7..53ec9b9d9bc4 100644
--- a/virt/kvm/arm/vgic/vgic-init.c
+++ b/virt/kvm/arm/vgic/vgic-init.c
@@ -348,6 +348,12 @@ void kvm_vgic_vcpu_destroy(struct kvm_vcpu *vcpu)
 {
 	struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;
 
+	/*
+	 * Retire all pending LPIs on this vcpu anyway as we're
+	 * going to destroy it.
+	 */
+	vgic_flush_pending_lpis(vcpu);
+
 	INIT_LIST_HEAD(&vgic_cpu->ap_list_head);
 }
 
-- 
2.19.1



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Re: [PATCH 1/2] KVM: arm64: vgic-v3: Retire all pending LPIs on vcpu destroy

[Marc Zyngier]

On Tue, 14 Apr 2020 11:03:47 +0800
Zenghui Yu <yuzenghui@huawei.com> wrote:

Hi Zenghui,

> It's likely that the vcpu fails to handle all virtual interrupts if
> userspace decides to destroy it, leaving the pending ones stay in the
> ap_list. If the un-handled one is a LPI, its vgic_irq structure will
> be eventually leaked because of an extra refcount increment in
> vgic_queue_irq_unlock().
> 
> This was detected by kmemleak on almost every guest destroy, the
> backtrace is as follows:
> 
> unreferenced object 0xffff80725aed5500 (size 128):
> comm "CPU 5/KVM", pid 40711, jiffies 4298024754 (age 166366.512s)
> hex dump (first 32 bytes):
> 00 00 00 00 00 00 00 00 08 01 a9 73 6d 80 ff ff ...........sm...
> c8 61 ee a9 00 20 ff ff 28 1e 55 81 6c 80 ff ff .a... ..(.U.l...
> backtrace:
> [<000000004bcaa122>] kmem_cache_alloc_trace+0x2dc/0x418
> [<0000000069c7dabb>] vgic_add_lpi+0x88/0x418
> [<00000000bfefd5c5>] vgic_its_cmd_handle_mapi+0x4dc/0x588
> [<00000000cf993975>] vgic_its_process_commands.part.5+0x484/0x1198
> [<000000004bd3f8e3>] vgic_its_process_commands+0x50/0x80
> [<00000000b9a65b2b>] vgic_mmio_write_its_cwriter+0xac/0x108
> [<0000000009641ebb>] dispatch_mmio_write+0xd0/0x188
> [<000000008f79d288>] __kvm_io_bus_write+0x134/0x240
> [<00000000882f39ac>] kvm_io_bus_write+0xe0/0x150
> [<0000000078197602>] io_mem_abort+0x484/0x7b8
> [<0000000060954e3c>] kvm_handle_guest_abort+0x4cc/0xa58
> [<00000000e0d0cd65>] handle_exit+0x24c/0x770
> [<00000000b44a7fad>] kvm_arch_vcpu_ioctl_run+0x460/0x1988
> [<0000000025fb897c>] kvm_vcpu_ioctl+0x4f8/0xee0
> [<000000003271e317>] do_vfs_ioctl+0x160/0xcd8
> [<00000000e7f39607>] ksys_ioctl+0x98/0xd8
> 
> Fix it by retiring all pending LPIs in the ap_list on the destroy path.
> 
> p.s. I can also reproduce it on a normal guest shutdown. It is because
> userspace still send LPIs to vcpu (through KVM_SIGNAL_MSI ioctl) while
> the guest is being shutdown and unable to handle it. A little strange
> though and haven't dig further...

What userspace are you using? You'd hope that the VMM would stop
processing I/Os when destroying the guest. But we still need to handle
it anyway, and I thing this fix makes sense.

> 
> Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
> ---
>  virt/kvm/arm/vgic/vgic-init.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/virt/kvm/arm/vgic/vgic-init.c b/virt/kvm/arm/vgic/vgic-init.c
> index a963b9d766b7..53ec9b9d9bc4 100644
> --- a/virt/kvm/arm/vgic/vgic-init.c
> +++ b/virt/kvm/arm/vgic/vgic-init.c
> @@ -348,6 +348,12 @@ void kvm_vgic_vcpu_destroy(struct kvm_vcpu *vcpu)
>  {
>  	struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;
>  
> +	/*
> +	 * Retire all pending LPIs on this vcpu anyway as we're
> +	 * going to destroy it.
> +	 */
> +	vgic_flush_pending_lpis(vcpu);
> +
>  	INIT_LIST_HEAD(&vgic_cpu->ap_list_head);
>  }
>  

I guess that at this stage, the INIT_LIST_HEAD() is superfluous, right?

Otherwise, looks good. If you agree with the above, I can fix that
locally, no need to resend this patch.

Thanks,

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

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Re: [PATCH 1/2] KVM: arm64: vgic-v3: Retire all pending LPIs on vcpu destroy

[Zenghui Yu]

Hi Marc,

On 2020/4/14 18:54, Marc Zyngier wrote:
> On Tue, 14 Apr 2020 11:03:47 +0800
> Zenghui Yu <yuzenghui@huawei.com> wrote:
> 
> Hi Zenghui,
> 
>> It's likely that the vcpu fails to handle all virtual interrupts if
>> userspace decides to destroy it, leaving the pending ones stay in the
>> ap_list. If the un-handled one is a LPI, its vgic_irq structure will
>> be eventually leaked because of an extra refcount increment in
>> vgic_queue_irq_unlock().
>>
>> This was detected by kmemleak on almost every guest destroy, the
>> backtrace is as follows:
>>
>> unreferenced object 0xffff80725aed5500 (size 128):
>> comm "CPU 5/KVM", pid 40711, jiffies 4298024754 (age 166366.512s)
>> hex dump (first 32 bytes):
>> 00 00 00 00 00 00 00 00 08 01 a9 73 6d 80 ff ff ...........sm...
>> c8 61 ee a9 00 20 ff ff 28 1e 55 81 6c 80 ff ff .a... ..(.U.l...
>> backtrace:
>> [<000000004bcaa122>] kmem_cache_alloc_trace+0x2dc/0x418
>> [<0000000069c7dabb>] vgic_add_lpi+0x88/0x418
>> [<00000000bfefd5c5>] vgic_its_cmd_handle_mapi+0x4dc/0x588
>> [<00000000cf993975>] vgic_its_process_commands.part.5+0x484/0x1198
>> [<000000004bd3f8e3>] vgic_its_process_commands+0x50/0x80
>> [<00000000b9a65b2b>] vgic_mmio_write_its_cwriter+0xac/0x108
>> [<0000000009641ebb>] dispatch_mmio_write+0xd0/0x188
>> [<000000008f79d288>] __kvm_io_bus_write+0x134/0x240
>> [<00000000882f39ac>] kvm_io_bus_write+0xe0/0x150
>> [<0000000078197602>] io_mem_abort+0x484/0x7b8
>> [<0000000060954e3c>] kvm_handle_guest_abort+0x4cc/0xa58
>> [<00000000e0d0cd65>] handle_exit+0x24c/0x770
>> [<00000000b44a7fad>] kvm_arch_vcpu_ioctl_run+0x460/0x1988
>> [<0000000025fb897c>] kvm_vcpu_ioctl+0x4f8/0xee0
>> [<000000003271e317>] do_vfs_ioctl+0x160/0xcd8
>> [<00000000e7f39607>] ksys_ioctl+0x98/0xd8
>>
>> Fix it by retiring all pending LPIs in the ap_list on the destroy path.
>>
>> p.s. I can also reproduce it on a normal guest shutdown. It is because
>> userspace still send LPIs to vcpu (through KVM_SIGNAL_MSI ioctl) while
>> the guest is being shutdown and unable to handle it. A little strange
>> though and haven't dig further...
> 
> What userspace are you using? You'd hope that the VMM would stop
> processing I/Os when destroying the guest. But we still need to handle
> it anyway, and I thing this fix makes sense.

I'm using Qemu (master) for debugging. Looks like an interrupt
corresponding to a virtio device configuration change, triggered after
all other devices had freed their irqs. Not sure if it's expected.

>>
>> Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
>> ---
>>   virt/kvm/arm/vgic/vgic-init.c | 6 ++++++
>>   1 file changed, 6 insertions(+)
>>
>> diff --git a/virt/kvm/arm/vgic/vgic-init.c b/virt/kvm/arm/vgic/vgic-init.c
>> index a963b9d766b7..53ec9b9d9bc4 100644
>> --- a/virt/kvm/arm/vgic/vgic-init.c
>> +++ b/virt/kvm/arm/vgic/vgic-init.c
>> @@ -348,6 +348,12 @@ void kvm_vgic_vcpu_destroy(struct kvm_vcpu *vcpu)
>>   {
>>   	struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;
>>   
>> +	/*
>> +	 * Retire all pending LPIs on this vcpu anyway as we're
>> +	 * going to destroy it.
>> +	 */
>> +	vgic_flush_pending_lpis(vcpu);
>> +
>>   	INIT_LIST_HEAD(&vgic_cpu->ap_list_head);
>>   }
>>   
> 
> I guess that at this stage, the INIT_LIST_HEAD() is superfluous, right?

I was just thinking that the ap_list_head may not be empty (besides LPI,
with other active or pending interrupts), so leave it unchanged.

> Otherwise, looks good. If you agree with the above, I can fix that
> locally, no need to resend this patch.

Thanks,
Zenghui


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Re: [PATCH 1/2] KVM: arm64: vgic-v3: Retire all pending LPIs on vcpu destroy

[Marc Zyngier]

On Tue, 14 Apr 2020 19:17:49 +0800
Zenghui Yu <yuzenghui@huawei.com> wrote:

> Hi Marc,
> 
> On 2020/4/14 18:54, Marc Zyngier wrote:
> > On Tue, 14 Apr 2020 11:03:47 +0800
> > Zenghui Yu <yuzenghui@huawei.com> wrote:
> > 
> > Hi Zenghui,
> >   
> >> It's likely that the vcpu fails to handle all virtual interrupts if
> >> userspace decides to destroy it, leaving the pending ones stay in the
> >> ap_list. If the un-handled one is a LPI, its vgic_irq structure will
> >> be eventually leaked because of an extra refcount increment in
> >> vgic_queue_irq_unlock().
> >>
> >> This was detected by kmemleak on almost every guest destroy, the
> >> backtrace is as follows:
> >>
> >> unreferenced object 0xffff80725aed5500 (size 128):
> >> comm "CPU 5/KVM", pid 40711, jiffies 4298024754 (age 166366.512s)
> >> hex dump (first 32 bytes):
> >> 00 00 00 00 00 00 00 00 08 01 a9 73 6d 80 ff ff ...........sm...
> >> c8 61 ee a9 00 20 ff ff 28 1e 55 81 6c 80 ff ff .a... ..(.U.l...
> >> backtrace:
> >> [<000000004bcaa122>] kmem_cache_alloc_trace+0x2dc/0x418
> >> [<0000000069c7dabb>] vgic_add_lpi+0x88/0x418
> >> [<00000000bfefd5c5>] vgic_its_cmd_handle_mapi+0x4dc/0x588
> >> [<00000000cf993975>] vgic_its_process_commands.part.5+0x484/0x1198
> >> [<000000004bd3f8e3>] vgic_its_process_commands+0x50/0x80
> >> [<00000000b9a65b2b>] vgic_mmio_write_its_cwriter+0xac/0x108
> >> [<0000000009641ebb>] dispatch_mmio_write+0xd0/0x188
> >> [<000000008f79d288>] __kvm_io_bus_write+0x134/0x240
> >> [<00000000882f39ac>] kvm_io_bus_write+0xe0/0x150
> >> [<0000000078197602>] io_mem_abort+0x484/0x7b8
> >> [<0000000060954e3c>] kvm_handle_guest_abort+0x4cc/0xa58
> >> [<00000000e0d0cd65>] handle_exit+0x24c/0x770
> >> [<00000000b44a7fad>] kvm_arch_vcpu_ioctl_run+0x460/0x1988
> >> [<0000000025fb897c>] kvm_vcpu_ioctl+0x4f8/0xee0
> >> [<000000003271e317>] do_vfs_ioctl+0x160/0xcd8
> >> [<00000000e7f39607>] ksys_ioctl+0x98/0xd8
> >>
> >> Fix it by retiring all pending LPIs in the ap_list on the destroy path.
> >>
> >> p.s. I can also reproduce it on a normal guest shutdown. It is because
> >> userspace still send LPIs to vcpu (through KVM_SIGNAL_MSI ioctl) while
> >> the guest is being shutdown and unable to handle it. A little strange
> >> though and haven't dig further...  
> > 
> > What userspace are you using? You'd hope that the VMM would stop
> > processing I/Os when destroying the guest. But we still need to handle
> > it anyway, and I thing this fix makes sense.  
> 
> I'm using Qemu (master) for debugging. Looks like an interrupt
> corresponding to a virtio device configuration change, triggered after
> all other devices had freed their irqs. Not sure if it's expected.
> 
> >>
> >> Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
> >> ---
> >>   virt/kvm/arm/vgic/vgic-init.c | 6 ++++++
> >>   1 file changed, 6 insertions(+)
> >>
> >> diff --git a/virt/kvm/arm/vgic/vgic-init.c b/virt/kvm/arm/vgic/vgic-init.c
> >> index a963b9d766b7..53ec9b9d9bc4 100644
> >> --- a/virt/kvm/arm/vgic/vgic-init.c
> >> +++ b/virt/kvm/arm/vgic/vgic-init.c
> >> @@ -348,6 +348,12 @@ void kvm_vgic_vcpu_destroy(struct kvm_vcpu *vcpu)
> >>   {
> >>   	struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;  
> >>   >> +	/*  
> >> +	 * Retire all pending LPIs on this vcpu anyway as we're
> >> +	 * going to destroy it.
> >> +	 */
> >> +	vgic_flush_pending_lpis(vcpu);
> >> +
> >>   	INIT_LIST_HEAD(&vgic_cpu->ap_list_head);
> >>   }  
> >>   > > I guess that at this stage, the INIT_LIST_HEAD() is superfluous, right?  
> 
> I was just thinking that the ap_list_head may not be empty (besides LPI,
> with other active or pending interrupts), so leave it unchanged.

It isn't clear what purpose this serves (the vcpus are about to be
freed, and so are the ap_lists), but I guess it doesn't hurt either.
I'll queue both patches.

Thanks,

	M.
-- 
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[PATCH 2/2] KVM: arm64: vgic-its: Fix memory leak on the error path of vgic_add_lpi()

[Zenghui Yu]

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);
+	}
 
 	return irq;
 }
-- 
2.19.1



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Re: [PATCH 2/2] KVM: arm64: vgic-its: Fix memory leak on the error path of vgic_add_lpi()

[Zenghui Yu]

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.

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


Thanks,
Zenghui


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Re: [PATCH 2/2] KVM: arm64: vgic-its: Fix memory leak on the error path of vgic_add_lpi()

[Marc Zyngier]

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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Re: [PATCH 2/2] KVM: arm64: vgic-its: Fix memory leak on the error path of vgic_add_lpi()

[Zenghui Yu]

On 2020/4/17 1:23, Marc Zyngier wrote:
> 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.

Agreed. Thanks for the fix!


Zenghui


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