Re: [PATCH v6] virtio-pci: Fix the crash that the vector was used after released.

[Cindy Lu <lulu@redhat.com>]

On Mon, Apr 15, 2024 at 4:32 PM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Fri, Apr 12, 2024 at 02:26:55PM +0800, Cindy Lu wrote:
> > During the booting process of the non-standard image, the behavior of the
> > called function in qemu is as follows:
> >
> > 1. vhost_net_stop() was triggered by guest image. This will call the function
> > virtio_pci_set_guest_notifiers() with assgin= false,
> > virtio_pci_set_guest_notifiers(） will release the irqfd for vector 0
> >
> > 2. virtio_reset() was triggered, this will set configure vector to VIRTIO_NO_VECTOR
> >
> > 3.vhost_net_start() was called (at this time, the configure vector is
> > still VIRTIO_NO_VECTOR) and then call virtio_pci_set_guest_notifiers() with
> > assgin=true, so the irqfd for vector 0 is still not "init" during this process
> >
> > 4. The system continues to boot and sets the vector back to 0. After that
> > msix_fire_vector_notifier() was triggered to unmask the vector 0 and  meet the crash
> >
> > To fix the issue, we need to support changing the vector after VIRTIO_CONFIG_S_DRIVER_OK is set.
> >
> > (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)
> >
> > Fixes: f9a09ca3ea ("vhost: add support for configure interrupt")
> > Cc: qemu-stable@nongnu.org
> >
>
> empty line not needed here
>
will fix this

> > Signed-off-by: Cindy Lu <lulu@redhat.com>
>
> Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
>
> It's guest triggerable so either we merge this before the release,
> or rely on stable process :(
>
thanks a lot for explain this, but I'm still not  very clear about this
do you mean this can not be merged before 2024-04-23?
https://wiki.qemu.org/Planning/9.0#Release_Schedule
Really Thanks for your help
thanks
cindy

> > ---
> >  hw/virtio/virtio-pci.c | 43 ++++++++++++++++++++++++++++++++++++++++--
> >  1 file changed, 41 insertions(+), 2 deletions(-)
> >
> > diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> > index 1a7039fb0c..f83ec92990 100644
> > --- a/hw/virtio/virtio-pci.c
> > +++ b/hw/virtio/virtio-pci.c
> > @@ -1423,6 +1423,36 @@ static int virtio_pci_add_mem_cap(VirtIOPCIProxy *proxy,
> >
> >      return offset;
> >  }
> > +static void virtio_pci_set_and_change_vector(VirtIODevice *vdev,
> > +                                             VirtIOPCIProxy *proxy,
> > +                                             int queue_no, uint16_t old_vector,
> > +                                             uint16_t new_vector)
> > +{
> > +    /*
> > +     * If the device uses irqfd and the vector changes after DRIVER_OK is
> > +     * set, we need to release the old vector and set up the new one.
> > +     * others just need to set the new vector to device
> > +     */
> > +    if ((vdev->status & VIRTIO_CONFIG_S_DRIVER_OK) &&
> > +        (msix_enabled(&proxy->pci_dev) && kvm_msi_via_irqfd_enabled())) {
> > +        if (old_vector != VIRTIO_NO_VECTOR) {
> > +            kvm_virtio_pci_vector_release_one(proxy, queue_no);
> > +        }
> > +    }
> > +    /*set the new vector to device*/
> > +    if (queue_no == VIRTIO_CONFIG_IRQ_IDX) {
> > +        vdev->config_vector = new_vector;
> > +    } else {
> > +        virtio_queue_set_vector(vdev, queue_no, new_vector);
> > +    }
> > +    /* if the new vector chanegd need to set it up */
>
> typo
>
sure will fix this
thanks

cindy
> > +    if ((vdev->status & VIRTIO_CONFIG_S_DRIVER_OK) &&
> > +        (msix_enabled(&proxy->pci_dev) && kvm_msi_via_irqfd_enabled())) {
> > +        if (new_vector != VIRTIO_NO_VECTOR) {
> > +            kvm_virtio_pci_vector_use_one(proxy, queue_no);
> > +        }
> > +    }
> > +}
> >
> >  int virtio_pci_add_shm_cap(VirtIOPCIProxy *proxy,
> >                             uint8_t bar, uint64_t offset, uint64_t length,
> > @@ -1570,7 +1600,12 @@ static void virtio_pci_common_write(void *opaque, hwaddr addr,
> >          } else {
> >              val = VIRTIO_NO_VECTOR;
> >          }
> > -        vdev->config_vector = val;
> > +        vector = vdev->config_vector;
> > +        /*check if need to change the vector*/
> > +        if (val != vector) {
> > +            virtio_pci_set_and_change_vector(vdev, proxy, VIRTIO_CONFIG_IRQ_IDX,
> > +                                             vector, val);
> > +        }
> >          break;
> >      case VIRTIO_PCI_COMMON_STATUS:
> >          if (!(val & VIRTIO_CONFIG_S_DRIVER_OK)) {
> > @@ -1610,7 +1645,11 @@ static void virtio_pci_common_write(void *opaque, hwaddr addr,
> >          } else {
> >              val = VIRTIO_NO_VECTOR;
> >          }
> > -        virtio_queue_set_vector(vdev, vdev->queue_sel, val);
> > +        /*check if need to change the vector*/
> > +        if (val != vector) {
> > +            virtio_pci_set_and_change_vector(vdev, proxy, vdev->queue_sel,
> > +                                             vector, val);
> > +        }
> >          break;
> >      case VIRTIO_PCI_COMMON_Q_ENABLE:
> >          if (val == 1) {
> > --
> > 2.43.0
>