* [PATCH 0/2] KVM: arm/arm64: vgic: A couple of memory leak fixes
@ 2019-06-06 10:58 Dave Martin
2019-06-06 10:58 ` [PATCH 1/2] KVM: arm/arm64: vgic: Fix kvm_device leak in vgic_its_destroy Dave Martin
2019-06-06 10:58 ` [PATCH 2/2] KVM: arm/arm64: vgic: Fix irq refcount leak in kvm_vgic_set_owner() Dave Martin
0 siblings, 2 replies; 5+ messages in thread
From: Dave Martin @ 2019-06-06 10:58 UTC (permalink / raw)
To: kvmarm; +Cc: Marc Zyngier, Andre Przywara, linux-arm-kernel
While using kmemleak to verify that the KVM SVE series wasn't
contributing any new memory leaks, I hit a couple of existing leaks to
do with vGIC irqs and the vGIC ITS that appear to have been there for
a while.
See the individual patches for details.
I'm not familiar with the affected code, so I may have overlooked
something.
Tested with qemu on ThunderX2.
Dave Martin (2):
KVM: arm/arm64: vgic: Fix kvm_device leak in vgic_its_destroy
KVM: arm/arm64: vgic: Fix irq refcount leak in kvm_vgic_set_owner()
virt/kvm/arm/vgic/vgic-its.c | 1 +
virt/kvm/arm/vgic/vgic.c | 1 +
2 files changed, 2 insertions(+)
--
2.1.4
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^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH 1/2] KVM: arm/arm64: vgic: Fix kvm_device leak in vgic_its_destroy
2019-06-06 10:58 [PATCH 0/2] KVM: arm/arm64: vgic: A couple of memory leak fixes Dave Martin
@ 2019-06-06 10:58 ` Dave Martin
2019-06-06 10:58 ` [PATCH 2/2] KVM: arm/arm64: vgic: Fix irq refcount leak in kvm_vgic_set_owner() Dave Martin
1 sibling, 0 replies; 5+ messages in thread
From: Dave Martin @ 2019-06-06 10:58 UTC (permalink / raw)
To: kvmarm; +Cc: Marc Zyngier, Andre Przywara, linux-arm-kernel
kvm_device->destroy() seems to be supposed to free its kvm_device
struct, but vgic_its_destroy() is not currently doing this,
resulting in a memory leak, resulting in kmemleak reports such as
the following:
unreferenced object 0xffff800aeddfe280 (size 128):
comm "qemu-system-aar", pid 13799, jiffies 4299827317 (age 1569.844s)
[...]
backtrace:
[<00000000a08b80e2>] kmem_cache_alloc+0x178/0x208
[<00000000dcad2bd3>] kvm_vm_ioctl+0x350/0xbc0
Fix it.
Cc: Andre Przywara <andre.przywara@arm.com>
Fixes: 1085fdc68c60 ("KVM: arm64: vgic-its: Introduce new KVM ITS device")
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
---
This was observed with native qemu on ThunderX2, on a merge of v5.1 with
kvmarm/next commit 9eecfc22e0bf ("KVM: arm64: Fix ptrauth ID register
masking logic"). This may not be a new regression, though.
My qemu invocation was:
$ qemu-system-aarch64 -machine virt,accel=kvm,gic_version=3 -cpu host \
-smp 4 -nographic \
-drive id=vblock,file=block.qcow2,format=qcow2,if=none \
-device virtio-blk-device,drive=vblock \
-kernel Image -append 'root=/dev/vda1 ro'
---
virt/kvm/arm/vgic/vgic-its.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
index 44ceaccb..8c9fe83 100644
--- a/virt/kvm/arm/vgic/vgic-its.c
+++ b/virt/kvm/arm/vgic/vgic-its.c
@@ -1734,6 +1734,7 @@ static void vgic_its_destroy(struct kvm_device *kvm_dev)
mutex_unlock(&its->its_lock);
kfree(its);
+ kfree(kvm_dev);/* alloc by kvm_ioctl_create_device, free by .destroy */
}
static int vgic_its_has_attr_regs(struct kvm_device *dev,
--
2.1.4
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^ permalink raw reply related [flat|nested] 5+ messages in thread
* [PATCH 2/2] KVM: arm/arm64: vgic: Fix irq refcount leak in kvm_vgic_set_owner()
2019-06-06 10:58 [PATCH 0/2] KVM: arm/arm64: vgic: A couple of memory leak fixes Dave Martin
2019-06-06 10:58 ` [PATCH 1/2] KVM: arm/arm64: vgic: Fix kvm_device leak in vgic_its_destroy Dave Martin
@ 2019-06-06 10:58 ` Dave Martin
2019-06-06 12:06 ` Marc Zyngier
1 sibling, 1 reply; 5+ messages in thread
From: Dave Martin @ 2019-06-06 10:58 UTC (permalink / raw)
To: kvmarm; +Cc: Marc Zyngier, Andre Przywara, linux-arm-kernel
kvm_vgic_set_owner() leaks a reference on the vgic_irq descriptor,
which does not seem to match up with any vgic_put_irq() that I can
find.
Since the irq pointer is not passed out and the caller must anyway
subsequently use vgic_get_irq() when is wants a pointer, it is not
clear why we should have a dangling refcount here.
The refcount is still needed inside kvm_vgic_set_owner() to prevent
the vgic_irq struct from disappearing while while it is
manipulated.
So, keep it vgic_get_irq() here, but add the matching
vgic_put_irq() before returning.
unreferenced object 0xffff800b6365ab80 (size 128):
comm "qemu-system-aar", pid 14414, jiffies 4300822606 (age 84.436s)
hex dump (first 32 bytes):
00 00 00 00 00 00 00 00 b0 e1 e0 38 00 00 ff ff ...........8....
b0 e1 e0 38 00 00 ff ff 78 e6 ad dd 0a 80 ff ff ...8....x.......
backtrace:
[<00000000a08b80e2>] kmem_cache_alloc+0x178/0x208
[<00000000114591cb>] vgic_add_lpi.part.5+0x34/0x190
[<00000000ec1425ae>] vgic_its_cmd_handle_mapi+0x320/0x348
[<00000000935c5c32>] vgic_its_process_commands.part.14+0x350/0x8b8
[<00000000dc256d2c>] vgic_mmio_write_its_cwriter+0x78/0x98
[<000000008659acd2>] dispatch_mmio_write+0xd4/0x120
[...]
Cc: Christoffer Dall <christoffer.dall@arm.com>
Fixes: c6ccd30e0de3 ("KVM: arm/arm64: Introduce an allocator for in-kernel irq lines")
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
---
Based on the limited testing I've done so far, the patch _appears_ to
fix the bug.
However, I still don't understand which the bug is intermittent, or why
the arch_timer or pmu (the only apparent users of kvm_vgic_set_owner())
are claiming an LPI in the first place.
So there may be other bugs in the mix, or I may have misunderstood
something...
The bug (and fix) were observed with native qemu on ThunderX2, on a
merge of v5.1 with kvmarm/next commit 9eecfc22e0bf ("KVM: arm64: Fix
ptrauth ID register masking logic").
My qemu invocation was:
$ qemu-system-aarch64 -machine virt,accel=kvm,gic_version=3 -cpu host \
-smp 4 -nographic \
-drive id=vblock,file=block.qcow2,format=qcow2,if=none \
-device virtio-blk-device,drive=vblock \
-kernel Image -append 'root=/dev/vda1 ro'
---
virt/kvm/arm/vgic/vgic.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c
index 191decc..930319c 100644
--- a/virt/kvm/arm/vgic/vgic.c
+++ b/virt/kvm/arm/vgic/vgic.c
@@ -599,6 +599,7 @@ int kvm_vgic_set_owner(struct kvm_vcpu *vcpu, unsigned int intid, void *owner)
else
irq->owner = owner;
raw_spin_unlock_irqrestore(&irq->irq_lock, flags);
+ vgic_put_irq(vcpu->kvm, irq);
return ret;
}
--
2.1.4
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^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH 2/2] KVM: arm/arm64: vgic: Fix irq refcount leak in kvm_vgic_set_owner()
2019-06-06 10:58 ` [PATCH 2/2] KVM: arm/arm64: vgic: Fix irq refcount leak in kvm_vgic_set_owner() Dave Martin
@ 2019-06-06 12:06 ` Marc Zyngier
2019-06-06 12:34 ` Dave Martin
0 siblings, 1 reply; 5+ messages in thread
From: Marc Zyngier @ 2019-06-06 12:06 UTC (permalink / raw)
To: Dave Martin, kvmarm; +Cc: Andre Przywara, linux-arm-kernel
On 06/06/2019 11:58, Dave Martin wrote:
> kvm_vgic_set_owner() leaks a reference on the vgic_irq descriptor,
> which does not seem to match up with any vgic_put_irq() that I can
> find.
>
> Since the irq pointer is not passed out and the caller must anyway
> subsequently use vgic_get_irq() when is wants a pointer, it is not
> clear why we should have a dangling refcount here.
>
> The refcount is still needed inside kvm_vgic_set_owner() to prevent
> the vgic_irq struct from disappearing while while it is
> manipulated.
>
> So, keep it vgic_get_irq() here, but add the matching
> vgic_put_irq() before returning.
>
> unreferenced object 0xffff800b6365ab80 (size 128):
> comm "qemu-system-aar", pid 14414, jiffies 4300822606 (age 84.436s)
> hex dump (first 32 bytes):
> 00 00 00 00 00 00 00 00 b0 e1 e0 38 00 00 ff ff ...........8....
> b0 e1 e0 38 00 00 ff ff 78 e6 ad dd 0a 80 ff ff ...8....x.......
> backtrace:
> [<00000000a08b80e2>] kmem_cache_alloc+0x178/0x208
> [<00000000114591cb>] vgic_add_lpi.part.5+0x34/0x190
> [<00000000ec1425ae>] vgic_its_cmd_handle_mapi+0x320/0x348
> [<00000000935c5c32>] vgic_its_process_commands.part.14+0x350/0x8b8
> [<00000000dc256d2c>] vgic_mmio_write_its_cwriter+0x78/0x98
> [<000000008659acd2>] dispatch_mmio_write+0xd4/0x120
>
> [...]
>
> Cc: Christoffer Dall <christoffer.dall@arm.com>
> Fixes: c6ccd30e0de3 ("KVM: arm/arm64: Introduce an allocator for in-kernel irq lines")
> Signed-off-by: Dave Martin <Dave.Martin@arm.com>
>
> ---
>
> Based on the limited testing I've done so far, the patch _appears_ to
> fix the bug.
>
> However, I still don't understand which the bug is intermittent, or why
> the arch_timer or pmu (the only apparent users of kvm_vgic_set_owner())
> are claiming an LPI in the first place.
>
> So there may be other bugs in the mix, or I may have misunderstood
> something...
Yeah, this doesn't make much sense. Both timer and PMU are using PPIs,
which are not refcounted, so this vgic_put_irq() is effectively a NOP.
It doesn't invalidate the patch itself, it is just that I seriously
doubt it fixes anything.
LPIs do not use the owner field so far, so we must have another get/put
mismatch somewhere.
Thanks,
M.
--
Jazz is not dead. It just smells funny...
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH 2/2] KVM: arm/arm64: vgic: Fix irq refcount leak in kvm_vgic_set_owner()
2019-06-06 12:06 ` Marc Zyngier
@ 2019-06-06 12:34 ` Dave Martin
0 siblings, 0 replies; 5+ messages in thread
From: Dave Martin @ 2019-06-06 12:34 UTC (permalink / raw)
To: Marc Zyngier; +Cc: Andre Przywara, kvmarm, linux-arm-kernel
On Thu, Jun 06, 2019 at 01:06:33PM +0100, Marc Zyngier wrote:
> On 06/06/2019 11:58, Dave Martin wrote:
> > kvm_vgic_set_owner() leaks a reference on the vgic_irq descriptor,
> > which does not seem to match up with any vgic_put_irq() that I can
> > find.
> >
> > Since the irq pointer is not passed out and the caller must anyway
> > subsequently use vgic_get_irq() when is wants a pointer, it is not
> > clear why we should have a dangling refcount here.
> >
> > The refcount is still needed inside kvm_vgic_set_owner() to prevent
> > the vgic_irq struct from disappearing while while it is
> > manipulated.
> >
> > So, keep it vgic_get_irq() here, but add the matching
> > vgic_put_irq() before returning.
> >
> > unreferenced object 0xffff800b6365ab80 (size 128):
> > comm "qemu-system-aar", pid 14414, jiffies 4300822606 (age 84.436s)
> > hex dump (first 32 bytes):
> > 00 00 00 00 00 00 00 00 b0 e1 e0 38 00 00 ff ff ...........8....
> > b0 e1 e0 38 00 00 ff ff 78 e6 ad dd 0a 80 ff ff ...8....x.......
> > backtrace:
> > [<00000000a08b80e2>] kmem_cache_alloc+0x178/0x208
> > [<00000000114591cb>] vgic_add_lpi.part.5+0x34/0x190
> > [<00000000ec1425ae>] vgic_its_cmd_handle_mapi+0x320/0x348
> > [<00000000935c5c32>] vgic_its_process_commands.part.14+0x350/0x8b8
> > [<00000000dc256d2c>] vgic_mmio_write_its_cwriter+0x78/0x98
> > [<000000008659acd2>] dispatch_mmio_write+0xd4/0x120
> >
> > [...]
> >
> > Cc: Christoffer Dall <christoffer.dall@arm.com>
> > Fixes: c6ccd30e0de3 ("KVM: arm/arm64: Introduce an allocator for in-kernel irq lines")
> > Signed-off-by: Dave Martin <Dave.Martin@arm.com>
> >
> > ---
> >
> > Based on the limited testing I've done so far, the patch _appears_ to
> > fix the bug.
> >
> > However, I still don't understand which the bug is intermittent, or why
> > the arch_timer or pmu (the only apparent users of kvm_vgic_set_owner())
> > are claiming an LPI in the first place.
> >
> > So there may be other bugs in the mix, or I may have misunderstood
> > something...
>
> Yeah, this doesn't make much sense. Both timer and PMU are using PPIs,
> which are not refcounted, so this vgic_put_irq() is effectively a NOP.
> It doesn't invalidate the patch itself, it is just that I seriously
> doubt it fixes anything.
>
> LPIs do not use the owner field so far, so we must have another get/put
> mismatch somewhere.
No argument from me.
As I say, this change _appeared_ to make this leak go away, but I
couldn't understand why, and didn't kick it very thoroughly. So it
may well be a red herring.
Cheers
---Dave
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2019-06-06 10:58 [PATCH 0/2] KVM: arm/arm64: vgic: A couple of memory leak fixes Dave Martin
2019-06-06 10:58 ` [PATCH 1/2] KVM: arm/arm64: vgic: Fix kvm_device leak in vgic_its_destroy Dave Martin
2019-06-06 10:58 ` [PATCH 2/2] KVM: arm/arm64: vgic: Fix irq refcount leak in kvm_vgic_set_owner() Dave Martin
2019-06-06 12:06 ` Marc Zyngier
2019-06-06 12:34 ` Dave Martin
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