Re: [PULL 1/1] virtio-pci: fix use of a released vector
On Tue, 16 Apr 2024 at 14:06, Cindy Lu wrote: > > On Tue, Apr 16, 2024 at 8:22 PM Peter Maydell > 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
On Tue, Apr 16, 2024 at 8:22 PM Peter Maydell wrote:
>
> On Tue, 16 Apr 2024 at 12:50, Peter Maydell wrote:
> >
> > On Tue, 16 Apr 2024 at 12:05, Cindy Lu wrote:
> > >
> > > On Tue, Apr 16, 2024 at 6:01 PM Peter Maydell
> > > 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
On Tue, Apr 16, 2024 at 7:50 PM Peter Maydell wrote:
>
> On Tue, 16 Apr 2024 at 12:05, Cindy Lu wrote:
> >
> > On Tue, Apr 16, 2024 at 6:01 PM Peter Maydell
> > 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 1/1] virtio-pci: fix use of a released vector
On Tue, 16 Apr 2024 at 12:50, Peter Maydell wrote:
>
> On Tue, 16 Apr 2024 at 12:05, Cindy Lu wrote:
> >
> > On Tue, Apr 16, 2024 at 6:01 PM Peter Maydell
> > 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
On Tue, 16 Apr 2024 at 12:05, Cindy Lu wrote:
>
> On Tue, Apr 16, 2024 at 6:01 PM Peter Maydell
> 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
On Tue, Apr 16, 2024 at 6:01 PM Peter Maydell wrote:
>
> On Mon, 15 Apr 2024 at 11:52, Michael S. Tsirkin wrote:
> >
> > From: Cindy Lu
> >
> > 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(>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
On Mon, 15 Apr 2024 at 11:52, Michael S. Tsirkin wrote:
>
> From: Cindy Lu
>
> 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(>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
