[PULL 0/1] virtio: bugfix

[PULL 0/1] virtio: bugfix

[Michael S. Tsirkin]

The following changes since commit e1999904a960c33b68fedf26dfb7b8e00abab8f2:

  qdev-monitor: fix error message in find_device_state() (2024-04-09 02:31:33 -0400)

are available in the Git repository at:

  https://git.kernel.org/pub/scm/virt/kvm/mst/qemu.git tags/for_upstream

for you to fetch changes up to 2ce6cff94df2650c460f809e5ad263f1d22507c0:

  virtio-pci: fix use of a released vector (2024-04-15 06:50:44 -0400)

----------------------------------------------------------------
virtio: bugfix

A last minute fix for a use of a vector after it's released.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

----------------------------------------------------------------
Cindy Lu (1):
      virtio-pci: fix use of a released vector

 hw/virtio/virtio-pci.c | 37 +++++++++++++++++++++++++++++++++++--
 1 file changed, 35 insertions(+), 2 deletions(-)

[PULL 1/1] virtio-pci: fix use of a released vector

[Michael S. Tsirkin]

From: Cindy Lu <lulu@redhat.com>

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)

MST: coding style and typo fixups

Fixes: f9a09ca3ea ("vhost: add support for configure interrupt")
Cc: qemu-stable@nongnu.org
Signed-off-by: Cindy Lu <lulu@redhat.com>
Message-ID: <2321ade5f601367efe7380c04e3f61379c59b48f.1713173550.git.mst@redhat.com>
Cc: Lei Yang <leiyang@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Tested-by: Cindy Lu <lulu@redhat.com>
---
 hw/virtio/virtio-pci.c | 37 +++++++++++++++++++++++++++++++++++--
 1 file changed, 35 insertions(+), 2 deletions(-)

diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
index cb6940fc0e..cb159fd078 100644
--- a/hw/virtio/virtio-pci.c
+++ b/hw/virtio/virtio-pci.c
@@ -1424,6 +1424,38 @@ static int virtio_pci_add_mem_cap(VirtIOPCIProxy *proxy,
     return offset;
 }
 
+static void virtio_pci_set_vector(VirtIODevice *vdev,
+                                  VirtIOPCIProxy *proxy,
+                                  int queue_no, uint16_t old_vector,
+                                  uint16_t new_vector)
+{
+    bool kvm_irqfd = (vdev->status & VIRTIO_CONFIG_S_DRIVER_OK) &&
+        msix_enabled(&proxy->pci_dev) && kvm_msi_via_irqfd_enabled();
+
+    if (new_vector == old_vector) {
+        return;
+    }
+
+    /*
+     * 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.
+     * Otherwise just need to set the new vector on the device.
+     */
+    if (kvm_irqfd && old_vector != VIRTIO_NO_VECTOR) {
+        kvm_virtio_pci_vector_release_one(proxy, queue_no);
+    }
+    /* Set the new vector on the 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 changed need to set it up. */
+    if (kvm_irqfd && 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,
                            uint8_t id)
@@ -1570,7 +1602,8 @@ static void virtio_pci_common_write(void *opaque, hwaddr addr,
         } else {
             val = VIRTIO_NO_VECTOR;
         }
-        vdev->config_vector = val;
+        virtio_pci_set_vector(vdev, proxy, VIRTIO_CONFIG_IRQ_IDX,
+                              vdev->config_vector, val);
         break;
     case VIRTIO_PCI_COMMON_STATUS:
         if (!(val & VIRTIO_CONFIG_S_DRIVER_OK)) {
@@ -1610,7 +1643,7 @@ static void virtio_pci_common_write(void *opaque, hwaddr addr,
         } else {
             val = VIRTIO_NO_VECTOR;
         }
-        virtio_queue_set_vector(vdev, vdev->queue_sel, val);
+        virtio_pci_set_vector(vdev, proxy, vdev->queue_sel, vector, val);
         break;
     case VIRTIO_PCI_COMMON_Q_ENABLE:
         if (val == 1) {
-- 
MST

Re: [PULL 1/1] virtio-pci: fix use of a released vector

[Peter Maydell]

On Mon, 15 Apr 2024 at 11:52, Michael S. Tsirkin <mst@redhat.com> wrote:
>
> From: Cindy Lu <lulu@redhat.com>
>
> 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.
>

Hi; Coverity points out what it thinks is a problem in this commit
(CID 1543938):

> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> index cb6940fc0e..cb159fd078 100644
> --- a/hw/virtio/virtio-pci.c
> +++ b/hw/virtio/virtio-pci.c
> @@ -1424,6 +1424,38 @@ static int virtio_pci_add_mem_cap(VirtIOPCIProxy *proxy,
>      return offset;
>  }
>
> +static void virtio_pci_set_vector(VirtIODevice *vdev,
> +                                  VirtIOPCIProxy *proxy,
> +                                  int queue_no, uint16_t old_vector,
> +                                  uint16_t new_vector)
> +{
> +    bool kvm_irqfd = (vdev->status & VIRTIO_CONFIG_S_DRIVER_OK) &&
> +        msix_enabled(&proxy->pci_dev) && kvm_msi_via_irqfd_enabled();
> +
> +    if (new_vector == old_vector) {
> +        return;
> +    }
> +
> +    /*
> +     * 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.
> +     * Otherwise just need to set the new vector on the device.
> +     */
> +    if (kvm_irqfd && old_vector != VIRTIO_NO_VECTOR) {
> +        kvm_virtio_pci_vector_release_one(proxy, queue_no);
> +    }
> +    /* Set the new vector on the device. */
> +    if (queue_no == VIRTIO_CONFIG_IRQ_IDX) {
> +        vdev->config_vector = new_vector;
> +    } else {
> +        virtio_queue_set_vector(vdev, queue_no, new_vector);
> +    }

Here queue_no can be VIRTIO_CONFIG_IRQ_IDX, which is -1.

> +    /* If the new vector changed need to set it up. */
> +    if (kvm_irqfd && new_vector != VIRTIO_NO_VECTOR) {
> +        kvm_virtio_pci_vector_use_one(proxy, queue_no);

Here we pass that through to kvm_virtio_pci_vector_use_one().
In kvm_virtio_pci_vector_use_one()'s error-exit path ("undo")
it does
    vector = virtio_queue_vector(vdev, queue_no);
and in virtio_queue_vector() it does:

    return n < VIRTIO_QUEUE_MAX ? vdev->vq[n].vector :
        VIRTIO_NO_VECTOR;

where 'n' is an int, so if we can get here with queue_no being
VIRTIO_CONFIG_IRQ_IDX then we'll index off the front of the
vdev->vq[] array.

Maybe this is a "can't happen" case, but it does seem odd that
virtio_queue_vector() only bounds-checks the "too big" case
for its argument and not the "too small" case and/or it
doesn't have a special case for VIRTIO_CONFIG_IRQ_IDX.

> +    }
> +}
> +

thanks
-- PMM

Re: [PULL 1/1] virtio-pci: fix use of a released vector

[Cindy Lu]

On Tue, Apr 16, 2024 at 6:01 PM Peter Maydell <peter.maydell@linaro.org> wrote:
>
> On Mon, 15 Apr 2024 at 11:52, Michael S. Tsirkin <mst@redhat.com> wrote:
> >
> > From: Cindy Lu <lulu@redhat.com>
> >
> > 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.
> >
>
> Hi; Coverity points out what it thinks is a problem in this commit
> (CID 1543938):
>
> > diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> > index cb6940fc0e..cb159fd078 100644
> > --- a/hw/virtio/virtio-pci.c
> > +++ b/hw/virtio/virtio-pci.c
> > @@ -1424,6 +1424,38 @@ static int virtio_pci_add_mem_cap(VirtIOPCIProxy *proxy,
> >      return offset;
> >  }
> >
> > +static void virtio_pci_set_vector(VirtIODevice *vdev,
> > +                                  VirtIOPCIProxy *proxy,
> > +                                  int queue_no, uint16_t old_vector,
> > +                                  uint16_t new_vector)
> > +{
> > +    bool kvm_irqfd = (vdev->status & VIRTIO_CONFIG_S_DRIVER_OK) &&
> > +        msix_enabled(&proxy->pci_dev) && kvm_msi_via_irqfd_enabled();
> > +
> > +    if (new_vector == old_vector) {
> > +        return;
> > +    }
> > +
> > +    /*
> > +     * 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.
> > +     * Otherwise just need to set the new vector on the device.
> > +     */
> > +    if (kvm_irqfd && old_vector != VIRTIO_NO_VECTOR) {
> > +        kvm_virtio_pci_vector_release_one(proxy, queue_no);
> > +    }
> > +    /* Set the new vector on the device. */
> > +    if (queue_no == VIRTIO_CONFIG_IRQ_IDX) {
> > +        vdev->config_vector = new_vector;
> > +    } else {
> > +        virtio_queue_set_vector(vdev, queue_no, new_vector);
> > +    }
>
> Here queue_no can be VIRTIO_CONFIG_IRQ_IDX, which is -1.
>
> > +    /* If the new vector changed need to set it up. */
> > +    if (kvm_irqfd && new_vector != VIRTIO_NO_VECTOR) {
> > +        kvm_virtio_pci_vector_use_one(proxy, queue_no);
>
> Here we pass that through to kvm_virtio_pci_vector_use_one().
> In kvm_virtio_pci_vector_use_one()'s error-exit path ("undo")
> it does
>     vector = virtio_queue_vector(vdev, queue_no);
> and in virtio_queue_vector() it does:
>
>     return n < VIRTIO_QUEUE_MAX ? vdev->vq[n].vector :
>         VIRTIO_NO_VECTOR;
>
> where 'n' is an int, so if we can get here with queue_no being
> VIRTIO_CONFIG_IRQ_IDX then we'll index off the front of the
> vdev->vq[] array.
>
> Maybe this is a "can't happen" case, but it does seem odd that
> virtio_queue_vector() only bounds-checks the "too big" case
> for its argument and not the "too small" case and/or it
> doesn't have a special case for VIRTIO_CONFIG_IRQ_IDX.
>
> > +    }
> > +}
> > +
>
hi peter
I think we can simply remove the part
    vector = virtio_queue_vector(vdev, queue_no);
the vector is get from virtio_pci_get_notifier() and don't need to get it again
I will send the fix soon
thanks
cindy
> thanks
> -- PMM
>

Re: [PULL 1/1] virtio-pci: fix use of a released vector

[Peter Maydell]

On Tue, 16 Apr 2024 at 12:05, Cindy Lu <lulu@redhat.com> wrote:
>
> On Tue, Apr 16, 2024 at 6:01 PM Peter Maydell <peter.maydell@linaro.org> wrote:
> > Here we pass that through to kvm_virtio_pci_vector_use_one().
> > In kvm_virtio_pci_vector_use_one()'s error-exit path ("undo")
> > it does
> >     vector = virtio_queue_vector(vdev, queue_no);
> > and in virtio_queue_vector() it does:
> >
> >     return n < VIRTIO_QUEUE_MAX ? vdev->vq[n].vector :
> >         VIRTIO_NO_VECTOR;
> >
> > where 'n' is an int, so if we can get here with queue_no being
> > VIRTIO_CONFIG_IRQ_IDX then we'll index off the front of the
> > vdev->vq[] array.
> >
> > Maybe this is a "can't happen" case, but it does seem odd that
> > virtio_queue_vector() only bounds-checks the "too big" case
> > for its argument and not the "too small" case and/or it
> > doesn't have a special case for VIRTIO_CONFIG_IRQ_IDX.
> >
> > > +    }
> > > +}
> > > +
> >
> hi peter
> I think we can simply remove the part
>     vector = virtio_queue_vector(vdev, queue_no);
> the vector is get from virtio_pci_get_notifier() and don't need to get it again
> I will send the fix soon

The error handling in kvm_virtio_pci_vector_use_one() looks
a bit odd in other ways, too. The only bit of "undoing"
it does as far as I can see is calling kvm_virtio_pci_irqfd_release(),
but there is no code path that gets to there where the
main codepath's call to kvm_virtio-pci_irqfd_use() succeeded
and needs to be undone. So perhaps the entire "undo" code
block should be deleted, and the "goto undo" lines
replaced by simple "return ret;" ?  (The codepath
for "kvm_virtio_pci_irqfd_use() failed" already does the
"kvm_virtio_pci_vq_vector_release()" by hand there.)

thanks
-- PMM

Re: [PULL 1/1] virtio-pci: fix use of a released vector

[Peter Maydell]

On Tue, 16 Apr 2024 at 12:50, Peter Maydell <peter.maydell@linaro.org> wrote:
>
> On Tue, 16 Apr 2024 at 12:05, Cindy Lu <lulu@redhat.com> wrote:
> >
> > On Tue, Apr 16, 2024 at 6:01 PM Peter Maydell <peter.maydell@linaro.org> wrote:
> > > Hi; Coverity points out what it thinks is a problem in
> > > this commit (CID 1543938):

> > > Here we pass that through to kvm_virtio_pci_vector_use_one().
> > > In kvm_virtio_pci_vector_use_one()'s error-exit path ("undo")
> > > it does
> > >     vector = virtio_queue_vector(vdev, queue_no);
> > > and in virtio_queue_vector() it does:
> > >
> > >     return n < VIRTIO_QUEUE_MAX ? vdev->vq[n].vector :
> > >         VIRTIO_NO_VECTOR;
> > >
> > > where 'n' is an int, so if we can get here with queue_no being
> > > VIRTIO_CONFIG_IRQ_IDX then we'll index off the front of the
> > > vdev->vq[] array.
> > >
> > > Maybe this is a "can't happen" case, but it does seem odd that
> > > virtio_queue_vector() only bounds-checks the "too big" case
> > > for its argument and not the "too small" case and/or it
> > > doesn't have a special case for VIRTIO_CONFIG_IRQ_IDX.
> > >
> > > > +    }
> > > > +}
> > > > +
> > >
> > hi peter
> > I think we can simply remove the part
> >     vector = virtio_queue_vector(vdev, queue_no);
> > the vector is get from virtio_pci_get_notifier() and don't need to get it again
> > I will send the fix soon
>
> The error handling in kvm_virtio_pci_vector_use_one() looks
> a bit odd in other ways, too. The only bit of "undoing"
> it does as far as I can see is calling kvm_virtio_pci_irqfd_release(),
> but there is no code path that gets to there where the
> main codepath's call to kvm_virtio-pci_irqfd_use() succeeded
> and needs to be undone. So perhaps the entire "undo" code
> block should be deleted, and the "goto undo" lines
> replaced by simple "return ret;" ?  (The codepath
> for "kvm_virtio_pci_irqfd_use() failed" already does the
> "kvm_virtio_pci_vq_vector_release()" by hand there.)

In any case since the error handling in kvm_virtio_pci_vector_use_one()
isn't new in this commit (you can get the same problem via
kvm_virtio_pci_vector_config_use(), which is CID 1468940
first detected in 2022), I think this is not something we need
to rush to fix before we release 9.0. If anybody disagrees now
would be a good time to say so :-)

Paolo's comment on CID 1468940 was to suggest "virtio_queue_vector
should check VIRTIO_CONFIG_IRQ_IDX just like virtio_pci_get_notifier",
incidentally.

thanks
-- PMM

Re: [PULL 1/1] virtio-pci: fix use of a released vector

[Cindy Lu]

On Tue, Apr 16, 2024 at 8:22 PM Peter Maydell <peter.maydell@linaro.org> wrote:
>
> On Tue, 16 Apr 2024 at 12:50, Peter Maydell <peter.maydell@linaro.org> wrote:
> >
> > On Tue, 16 Apr 2024 at 12:05, Cindy Lu <lulu@redhat.com> wrote:
> > >
> > > On Tue, Apr 16, 2024 at 6:01 PM Peter Maydell <peter.maydell@linaro.org> wrote:
> > > > Hi; Coverity points out what it thinks is a problem in
> > > > this commit (CID 1543938):
>
> > > > Here we pass that through to kvm_virtio_pci_vector_use_one().
> > > > In kvm_virtio_pci_vector_use_one()'s error-exit path ("undo")
> > > > it does
> > > >     vector = virtio_queue_vector(vdev, queue_no);
> > > > and in virtio_queue_vector() it does:
> > > >
> > > >     return n < VIRTIO_QUEUE_MAX ? vdev->vq[n].vector :
> > > >         VIRTIO_NO_VECTOR;
> > > >
> > > > where 'n' is an int, so if we can get here with queue_no being
> > > > VIRTIO_CONFIG_IRQ_IDX then we'll index off the front of the
> > > > vdev->vq[] array.
> > > >
> > > > Maybe this is a "can't happen" case, but it does seem odd that
> > > > virtio_queue_vector() only bounds-checks the "too big" case
> > > > for its argument and not the "too small" case and/or it
> > > > doesn't have a special case for VIRTIO_CONFIG_IRQ_IDX.
> > > >
> > > > > +    }
> > > > > +}
> > > > > +
> > > >
> > > hi peter
> > > I think we can simply remove the part
> > >     vector = virtio_queue_vector(vdev, queue_no);
> > > the vector is get from virtio_pci_get_notifier() and don't need to get it again
> > > I will send the fix soon
> >
> > The error handling in kvm_virtio_pci_vector_use_one() looks
> > a bit odd in other ways, too. The only bit of "undoing"
> > it does as far as I can see is calling kvm_virtio_pci_irqfd_release(),
> > but there is no code path that gets to there where the
> > main codepath's call to kvm_virtio-pci_irqfd_use() succeeded
> > and needs to be undone. So perhaps the entire "undo" code
> > block should be deleted, and the "goto undo" lines
> > replaced by simple "return ret;" ?  (The codepath
> > for "kvm_virtio_pci_irqfd_use() failed" already does the
> > "kvm_virtio_pci_vq_vector_release()" by hand there.)
>
> In any case since the error handling in kvm_virtio_pci_vector_use_one()
> isn't new in this commit (you can get the same problem via
> kvm_virtio_pci_vector_config_use(), which is CID 1468940
> first detected in 2022), I think this is not something we need
> to rush to fix before we release 9.0. If anybody disagrees now
> would be a good time to say so :-)
>
> Paolo's comment on CID 1468940 was to suggest "virtio_queue_vector
> should check VIRTIO_CONFIG_IRQ_IDX just like virtio_pci_get_notifier",
> incidentally.
>
Hi peter，
Really sorry all these mess, but I still have a stuipid question,
where can I get
this CID result ?maybe there are a mailing list？I just wonder maybe I can fix
these code earlier next time, Really thanks for your help

thanks
cindy
> thanks
> -- PMM
>

Re: [PULL 1/1] virtio-pci: fix use of a released vector

[Peter Maydell]

On Tue, 16 Apr 2024 at 14:06, Cindy Lu <lulu@redhat.com> wrote:
>
> On Tue, Apr 16, 2024 at 8:22 PM Peter Maydell <peter.maydell@linaro.org> wrote:
> > Paolo's comment on CID 1468940 was to suggest "virtio_queue_vector
> > should check VIRTIO_CONFIG_IRQ_IDX just like virtio_pci_get_notifier",
> > incidentally.
> >
> Hi peter，
> Really sorry all these mess, but I still have a stuipid question,
> where can I get
> this CID result ?maybe there are a mailing list？I just wonder maybe I can fix
> these code earlier next time, Really thanks for your help

These CID numbers are the identifiers of the issues in the
Coverity Scan online UI: https://scan.coverity.com/projects/qemu
You need to apply for access but we give that to anybody who's
a QEMU developer.

Unfortunately we can only do a very limited amount of Coverity
Scan runs (about one a day), so we run them only on code that
has been committed to QEMU already, and we aren't able to use
it to find problems in patches before we apply them.

thanks
-- PMM

Re: [PULL 1/1] virtio-pci: fix use of a released vector

[Cindy Lu]

On Tue, Apr 16, 2024 at 7:50 PM Peter Maydell <peter.maydell@linaro.org> wrote:
>
> On Tue, 16 Apr 2024 at 12:05, Cindy Lu <lulu@redhat.com> wrote:
> >
> > On Tue, Apr 16, 2024 at 6:01 PM Peter Maydell <peter.maydell@linaro.org> wrote:
> > > Here we pass that through to kvm_virtio_pci_vector_use_one().
> > > In kvm_virtio_pci_vector_use_one()'s error-exit path ("undo")
> > > it does
> > >     vector = virtio_queue_vector(vdev, queue_no);
> > > and in virtio_queue_vector() it does:
> > >
> > >     return n < VIRTIO_QUEUE_MAX ? vdev->vq[n].vector :
> > >         VIRTIO_NO_VECTOR;
> > >
> > > where 'n' is an int, so if we can get here with queue_no being
> > > VIRTIO_CONFIG_IRQ_IDX then we'll index off the front of the
> > > vdev->vq[] array.
> > >
> > > Maybe this is a "can't happen" case, but it does seem odd that
> > > virtio_queue_vector() only bounds-checks the "too big" case
> > > for its argument and not the "too small" case and/or it
> > > doesn't have a special case for VIRTIO_CONFIG_IRQ_IDX.
> > >
> > > > +    }
> > > > +}
> > > > +
> > >
> > hi peter
> > I think we can simply remove the part
> >     vector = virtio_queue_vector(vdev, queue_no);
> > the vector is get from virtio_pci_get_notifier() and don't need to get it again
> > I will send the fix soon
>
> The error handling in kvm_virtio_pci_vector_use_one() looks
> a bit odd in other ways, too. The only bit of "undoing"
> it does as far as I can see is calling kvm_virtio_pci_irqfd_release(),
> but there is no code path that gets to there where the
> main codepath's call to kvm_virtio-pci_irqfd_use() succeeded
> and needs to be undone. So perhaps the entire "undo" code
> block should be deleted, and the "goto undo" lines
> replaced by simple "return ret;" ?  (The codepath
> for "kvm_virtio_pci_irqfd_use() failed" already does the
> "kvm_virtio_pci_vq_vector_release()" by hand there.)
>
> thanks
> -- PMM
>
Hi peter,
Really thanks for your help. I have rewrite this part, the error
handling part is incorrect
Thanks
Cindy

Re: [PULL 0/1] virtio: bugfix

[Peter Maydell]

On Mon, 15 Apr 2024 at 11:52, Michael S. Tsirkin <mst@redhat.com> wrote:
>
> The following changes since commit e1999904a960c33b68fedf26dfb7b8e00abab8f2:
>
>   qdev-monitor: fix error message in find_device_state() (2024-04-09 02:31:33 -0400)
>
> are available in the Git repository at:
>
>   https://git.kernel.org/pub/scm/virt/kvm/mst/qemu.git tags/for_upstream
>
> for you to fetch changes up to 2ce6cff94df2650c460f809e5ad263f1d22507c0:
>
>   virtio-pci: fix use of a released vector (2024-04-15 06:50:44 -0400)
>
> ----------------------------------------------------------------
> virtio: bugfix
>
> A last minute fix for a use of a vector after it's released.
>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
>
> ----------------------------------------------------------------


Applied, thanks.

Please update the changelog at https://wiki.qemu.org/ChangeLog/9.0
for any user-visible changes.

-- PMM