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Re: [PATCH v2] kvm: Fix crash due to access uninitialized kvm_state
From: |
Peter Maydell |
Subject: |
Re: [PATCH v2] kvm: Fix crash due to access uninitialized kvm_state |
Date: |
Mon, 31 Jul 2023 14:19:58 +0100 |
On Mon, 31 Jul 2023 at 14:00, David Hildenbrand <david@redhat.com> wrote:
>
> On 31.07.23 14:59, Gavin Shan wrote:
> > Runs into core dump on arm64 and the backtrace extracted from the
> > core dump is shown as below. It's caused by accessing uninitialized
> > @kvm_state in kvm_flush_coalesced_mmio_buffer() due to commit 176d073029
> > ("hw/arm/virt: Use machine_memory_devices_init()"), where the machine's
> > memory region is added earlier than before.
> >
> > main
> > qemu_init
> > configure_accelerators
> > qemu_opts_foreach
> > do_configure_accelerator
> > accel_init_machine
> > kvm_init
> > virt_kvm_type
> > virt_set_memmap
> > machine_memory_devices_init
> > memory_region_add_subregion
> > memory_region_add_subregion_common
> > memory_region_update_container_subregions
> > memory_region_transaction_begin
> > qemu_flush_coalesced_mmio_buffer
> > kvm_flush_coalesced_mmio_buffer
> >
> > Fix it by bailing early in kvm_flush_coalesced_mmio_buffer() on the
> > uninitialized @kvm_state. With this applied, no crash is observed on
> > arm64.
> >
> > Fixes: 176d073029 ("hw/arm/virt: Use machine_memory_devices_init()")
> > Signed-off-by: Gavin Shan <gshan@redhat.com>
> > ---
> > v2: Bail early in kvm_flush_coalesced_mmio_buffer() on the uninitialized
> > @kvm_state and improved changelog (David/Peter)
> > ---
> > accel/kvm/kvm-all.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
> > index 373d876c05..7b3da8dc3a 100644
> > --- a/accel/kvm/kvm-all.c
> > +++ b/accel/kvm/kvm-all.c
> > @@ -2812,7 +2812,7 @@ void kvm_flush_coalesced_mmio_buffer(void)
> > {
> > KVMState *s = kvm_state;
> >
> > - if (s->coalesced_flush_in_progress) {
> > + if (!s || s->coalesced_flush_in_progress) {
> > return;
> > }
> >
>
> Thanks Gavin!
>
> Reviewed-by: David Hildenbrand <david@redhat.com>
Applied to target-arm.next, thanks.
-- PMM