Hi James,
Thanks for the heads up.
On 2020-04-23 12:35, James Morse wrote:
Hi Marc, Zenghui,
On 22/04/2020 17:18, Marc Zyngier wrote:
From: Zenghui Yu <yuzenghui@xxxxxxxxxx>
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().
diff --git a/virt/kvm/arm/vgic/vgic-init.c
b/virt/kvm/arm/vgic/vgic-init.c
index a963b9d766b73..53ec9b9d9bc43 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.
+ */
Looking at the other caller, do we need something like:
| if (vgic_cpu->lpis_enabled)
?
Huh... On its own, this call is absolutely harmless even if you
don't have LPIs. But see below.
+ vgic_flush_pending_lpis(vcpu);
+
Otherwise, I get this on a gic-v2 machine!:
[ 1742.187139] BUG: KASAN: use-after-free in
vgic_flush_pending_lpis+0x250/0x2c0
[ 1742.194302] Read of size 8 at addr ffff0008e1bf1f28 by task
qemu-system-aar/542
[ 1742.203140] CPU: 2 PID: 542 Comm: qemu-system-aar Not tainted
5.7.0-rc2-00006-g4fb0f7bb0e27 #2
[ 1742.211780] Hardware name: ARM LTD ARM Juno Development
Platform/ARM Juno Development
Platform, BIOS EDK II Jul 30 2018
[ 1742.222596] Call trace:
[ 1742.225059] dump_backtrace+0x0/0x328
[ 1742.228738] show_stack+0x18/0x28
[ 1742.232071] dump_stack+0x134/0x1b0
[ 1742.235578] print_address_description.isra.0+0x6c/0x350
[ 1742.240910] __kasan_report+0x10c/0x180
[ 1742.244763] kasan_report+0x4c/0x68
[ 1742.248268] __asan_report_load8_noabort+0x30/0x48
[ 1742.253081] vgic_flush_pending_lpis+0x250/0x2c0
[ 1742.257718] __kvm_vgic_destroy+0x1cc/0x478
[ 1742.261919] kvm_vgic_destroy+0x30/0x48
[ 1742.265773] kvm_arch_destroy_vm+0x20/0x128
[ 1742.269976] kvm_put_kvm+0x3e0/0x8d0
[ 1742.273567] kvm_vm_release+0x3c/0x60
[ 1742.277248] __fput+0x218/0x630
[ 1742.280406] ____fput+0x10/0x20
[ 1742.283565] task_work_run+0xd8/0x1f0
[ 1742.287245] do_exit+0x87c/0x2640
[ 1742.290575] do_group_exit+0xd0/0x258
[ 1742.294254] __arm64_sys_exit_group+0x3c/0x48
[ 1742.298631] el0_svc_common.constprop.0+0x10c/0x348
[ 1742.303529] do_el0_svc+0x48/0xd0
[ 1742.306861] el0_sync_handler+0x11c/0x1b8
[ 1742.310888] el0_sync+0x158/0x180
[ 1742.315716] The buggy address belongs to the page:
[ 1742.320529] page:fffffe002366fc40 refcount:0 mapcount:0
mapping:000000007e21d29f index:0x0
[ 1742.328821] flags: 0x2ffff00000000000()
[ 1742.332678] raw: 2ffff00000000000 0000000000000000 ffffffff23660401
0000000000000000
[ 1742.340449] raw: 0000000000000000 0000000000000000 00000000ffffffff
0000000000000000
[ 1742.348215] page dumped because: kasan: bad access detected
[ 1742.355304] Memory state around the buggy address:
[ 1742.360115] ffff0008e1bf1e00: ff ff ff ff ff ff ff ff ff ff ff ff
ff ff ff ff
[ 1742.367360] ffff0008e1bf1e80: ff ff ff ff ff ff ff ff ff ff ff ff
ff ff ff ff
[ 1742.374606] >ffff0008e1bf1f00: ff ff ff ff ff ff ff ff ff ff ff ff
ff ff ff ff
[ 1742.381851] ^
[ 1742.386399] ffff0008e1bf1f80: ff ff ff ff ff ff ff ff ff ff ff ff
ff ff ff ff
[ 1742.393645] ffff0008e1bf2000: ff ff ff ff ff ff ff ff ff ff ff ff
ff ff ff ff
[ 1742.400889]
==================================================================
[ 1742.408132] Disabling lock debugging due to kernel taint
With that:
Reviewed-by: James Morse <james.morse@xxxxxxx>
I think this is slightly more concerning. The issue is that we have
started freeing parts of the interrupt state already (we free the
SPIs early in kvm_vgic_dist_destroy()).
If a SPI was pending or active at this stage (i.e. present in the
ap_list), we are going to iterate over memory that has been freed
already. This is bad, and this can happen on GICv3 as well.
I think this should solve it, but I need to test it on a GICv2 system:
diff --git a/virt/kvm/arm/vgic/vgic-init.c
b/virt/kvm/arm/vgic/vgic-init.c
index 53ec9b9d9bc43..30dbec9fe0b4a 100644
--- a/virt/kvm/arm/vgic/vgic-init.c
+++ b/virt/kvm/arm/vgic/vgic-init.c
@@ -365,10 +365,10 @@ static void __kvm_vgic_destroy(struct kvm *kvm)
vgic_debug_destroy(kvm);
- kvm_vgic_dist_destroy(kvm);
-
kvm_for_each_vcpu(i, vcpu, kvm)
kvm_vgic_vcpu_destroy(vcpu);
+
+ kvm_vgic_dist_destroy(kvm);
}
void kvm_vgic_destroy(struct kvm *kvm)
Thanks,
M.
--
Jazz is not dead. It just smells funny...
