Re: [PATCH v2 1/1] virtio-pci: Fix the crash that the vector was used after released.

[Cindy Lu <lulu@redhat.com>]

On Wed, Apr 10, 2024 at 1:36 PM Jason Wang <jasowang@redhat.com> wrote:
>
> On Wed, Apr 10, 2024 at 1:29 PM Cindy Lu <lulu@redhat.com> wrote:
> >
> > When the guest triggers vhost_stop and then virtio_reset, the vector will the
> > IRQFD for this vector will be released and change to VIRTIO_NO_VECTOR.
> > After that, the guest called vhost_net_start,  (at this time, the configure
> > vector is still VIRTIO_NO_VECTOR),  vector 0 still was not "init".
> > The guest system continued to boot, set the vector back to 0, and then met the crash.
> >
> > To fix this, we need to call the function "kvm_virtio_pci_vector_use_one()"
> > when the vector changes back from VIRTIO_NO_VECTOR
> >
> > (gdb) bt
> > 0  __pthread_kill_implementation (threadid=<optimized out>, signo=signo@entry=6, no_tid=no_tid@entry=0)
> >     at pthread_kill.c:44
> > 1  0x00007fc87148ec53 in __pthread_kill_internal (signo=6, threadid=<optimized out>) at pthread_kill.c:78
> > 2  0x00007fc87143e956 in __GI_raise (sig=sig@entry=6) at ../sysdeps/posix/raise.c:26
> > 3  0x00007fc8714287f4 in __GI_abort () at abort.c:79
> > 4  0x00007fc87142871b in __assert_fail_base
> >     (fmt=0x7fc8715bbde0 "%s%s%s:%u: %s%sAssertion `%s' failed.\n%n", assertion=0x5606413efd53 "ret == 0", file=0x5606413ef87d "../accel/kvm/kvm-all.c", line=1837, function=<optimized out>) at assert.c:92
> > 5  0x00007fc871437536 in __GI___assert_fail
> >     (assertion=0x5606413efd53 "ret == 0", file=0x5606413ef87d "../accel/kvm/kvm-all.c", line=1837, function=0x5606413f06f0 <__PRETTY_FUNCTION__.19> "kvm_irqchip_commit_routes") at assert.c:101
> > 6  0x0000560640f884b5 in kvm_irqchip_commit_routes (s=0x560642cae1f0) at ../accel/kvm/kvm-all.c:1837
> > 7  0x0000560640c98f8e in virtio_pci_one_vector_unmask
> >     (proxy=0x560643c65f00, queue_no=4294967295, vector=0, msg=..., n=0x560643c6e4c8)
> >     at ../hw/virtio/virtio-pci.c:1005
> > 8  0x0000560640c99201 in virtio_pci_vector_unmask (dev=0x560643c65f00, vector=0, msg=...)
> >     at ../hw/virtio/virtio-pci.c:1070
> > 9  0x0000560640bc402e in msix_fire_vector_notifier (dev=0x560643c65f00, vector=0, is_masked=false)
> >     at ../hw/pci/msix.c:120
> > 10 0x0000560640bc40f1 in msix_handle_mask_update (dev=0x560643c65f00, vector=0, was_masked=true)
> >     at ../hw/pci/msix.c:140
> > 11 0x0000560640bc4503 in msix_table_mmio_write (opaque=0x560643c65f00, addr=12, val=0, size=4)
> >     at ../hw/pci/msix.c:231
> > 12 0x0000560640f26d83 in memory_region_write_accessor
> >     (mr=0x560643c66540, addr=12, value=0x7fc86b7bc628, size=4, shift=0, mask=4294967295, attrs=...)
> >     at ../system/memory.c:497
> > 13 0x0000560640f270a6 in access_with_adjusted_size
> >
> >      (addr=12, value=0x7fc86b7bc628, size=4, access_size_min=1, access_size_max=4, access_fn=0x560640f26c8d <memory_region_write_accessor>, mr=0x560643c66540, attrs=...) at ../system/memory.c:573
> > 14 0x0000560640f2a2b5 in memory_region_dispatch_write (mr=0x560643c66540, addr=12, data=0, op=MO_32, attrs=...)
> >     at ../system/memory.c:1521
> > 15 0x0000560640f37bac in flatview_write_continue
> >     (fv=0x7fc65805e0b0, addr=4273803276, attrs=..., ptr=0x7fc871e9c028, len=4, addr1=12, l=4, mr=0x560643c66540)
> >     at ../system/physmem.c:2714
> > 16 0x0000560640f37d0f in flatview_write
> >     (fv=0x7fc65805e0b0, addr=4273803276, attrs=..., buf=0x7fc871e9c028, len=4) at ../system/physmem.c:2756
> > 17 0x0000560640f380bf in address_space_write
> >     (as=0x560642161ae0 <address_space_memory>, addr=4273803276, attrs=..., buf=0x7fc871e9c028, len=4)
> >     at ../system/physmem.c:2863
> > 18 0x0000560640f3812c in address_space_rw
> >     (as=0x560642161ae0 <address_space_memory>, addr=4273803276, attrs=..., buf=0x7fc871e9c028, len=4, is_write=true) at ../system/physmem.c:2873
> > --Type <RET> for more, q to quit, c to continue without paging--
> > 19 0x0000560640f8aa55 in kvm_cpu_exec (cpu=0x560642f205e0) at ../accel/kvm/kvm-all.c:2915
> > 20 0x0000560640f8d731 in kvm_vcpu_thread_fn (arg=0x560642f205e0) at ../accel/kvm/kvm-accel-ops.c:51
> > 21 0x00005606411949f4 in qemu_thread_start (args=0x560642f292b0) at ../util/qemu-thread-posix.c:541
> > 22 0x00007fc87148cdcd in start_thread (arg=<optimized out>) at pthread_create.c:442
> > 23 0x00007fc871512630 in clone3 () at ../sysdeps/unix/sysv/linux/x86_64/clone3.S:81
> > (gdb)
> > Signed-off-by: Cindy Lu <lulu@redhat.com>
> > ---
> >  hw/virtio/virtio-pci.c | 35 +++++++++++++++++++++++++++++++++++
> >  1 file changed, 35 insertions(+)
> >
> > diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> > index 1a7039fb0c..344f4fb844 100644
> > --- a/hw/virtio/virtio-pci.c
> > +++ b/hw/virtio/virtio-pci.c
> > @@ -880,6 +880,7 @@ static int kvm_virtio_pci_vector_use_one(VirtIOPCIProxy *proxy, int queue_no)
> >      int ret;
> >      EventNotifier *n;
> >      PCIDevice *dev = &proxy->pci_dev;
> > +    VirtIOIRQFD *irqfd;
> >      VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus);
> >      VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
> >
> > @@ -890,10 +891,19 @@ static int kvm_virtio_pci_vector_use_one(VirtIOPCIProxy *proxy, int queue_no)
> >      if (vector >= msix_nr_vectors_allocated(dev)) {
> >          return 0;
> >      }
> > +    /*
> > +     * if the irqfd still in use, means the irqfd was not
> > +     * release before and don't need to set up
> > +     */
> > +    irqfd = &proxy->vector_irqfd[vector];
> > +    if (irqfd->users != 0) {
> > +        return 0;
> > +    }
>
> kvm_virtio_pci_vq_vector_use() has a similar check and it looks to me
> kvm_virtio_pci_irqfd_use() can work when users > 0.
>
> Any reason we need an extra check here?
>
> Thanks
>
in function kvm_virtio_pci_vq_vector_use(). this will not init the
irqfd, but there will be an
    irqfd->users++;
so the user number will be wrong in this irqfd, There will be check
for this in other function
sunch like kvm_virtio_pci_vq_vector_release()
{
    VirtIOIRQFD *irqfd = &proxy->vector_irqfd[vector];

    if (--irqfd->users == 0) {
        kvm_irqchip_release_virq(kvm_state, irqfd->virq);
    }
}
this will cause problem
thanks
Cindy


> >      ret = kvm_virtio_pci_vq_vector_use(proxy, vector);
> >      if (ret < 0) {
> >          goto undo;
> >      }
> > +
> >      /*
> >       * If guest supports masking, set up irqfd now.
> >       * Otherwise, delay until unmasked in the frontend.
> > @@ -1570,7 +1580,19 @@ static void virtio_pci_common_write(void *opaque, hwaddr addr,
> >          } else {
> >              val = VIRTIO_NO_VECTOR;
> >          }
> > +        vector = vdev->config_vector;
> >          vdev->config_vector = val;
> > +        /*
> > +         *if the val was change from NO_VECTOR, this means the vector maybe
> > +         * release before, need to check if need to set up
> > +         */
> > +        if ((val != VIRTIO_NO_VECTOR) && (vector == VIRTIO_NO_VECTOR) &&
> > +            (vdev->status & VIRTIO_CONFIG_S_DRIVER_OK)) {
> > +            /* check if use irqfd*/
> > +            if (msix_enabled(&proxy->pci_dev) && kvm_msi_via_irqfd_enabled()) {
> > +                kvm_virtio_pci_vector_use_one(proxy, VIRTIO_CONFIG_IRQ_IDX);
> > +            }
> > +        }
> >          break;
> >      case VIRTIO_PCI_COMMON_STATUS:
> >          if (!(val & VIRTIO_CONFIG_S_DRIVER_OK)) {
> > @@ -1611,6 +1633,19 @@ static void virtio_pci_common_write(void *opaque, hwaddr addr,
> >              val = VIRTIO_NO_VECTOR;
> >          }
> >          virtio_queue_set_vector(vdev, vdev->queue_sel, val);
> > +
> > +        /*
> > +         *if the val was change from NO_VECTOR, this means the vector maybe
> > +         * release before, need to check if need to set up
> > +         */
> > +
> > +        if ((val != VIRTIO_NO_VECTOR) && (vector == VIRTIO_NO_VECTOR) &&
> > +            (vdev->status & VIRTIO_CONFIG_S_DRIVER_OK)) {
> > +            /* check if use irqfd*/
> > +            if (msix_enabled(&proxy->pci_dev) && kvm_msi_via_irqfd_enabled()) {
> > +                kvm_virtio_pci_vector_use_one(proxy, vdev->queue_sel);
> > +            }
> > +        }
> >          break;
> >      case VIRTIO_PCI_COMMON_Q_ENABLE:
> >          if (val == 1) {
> > --
> > 2.43.0
> >
>