[v2] hw/net/vmxnet3: allow VMXNET3_MAX_MTU itself as a value

Currently, VMXNET3_MAX_MTU itself (being 9000) is not considered a
valid value for the MTU, but a guest running ESXi 7.0 might try to
set it and fail the assert [0].

In the Linux kernel, dev->max_mtu itself is a valid value for the MTU
and for the vmxnet3 driver it's 9000, so a guest running Linux will
also fail the assert when trying to set an MTU of 9000.

VMXNET3_MAX_MTU and s->mtu don't seem to be used in relation to buffer
allocations/accesses, so allowing the upper limit itself as a value
should be fine.

[0]: https://forum.proxmox.com/threads/114011/

Fixes: d05dcd94ae ("net: vmxnet3: validate configuration values during activate (CVE-2021-20203)")
Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
---

Feel free to adapt the commit message as you see fit.

v1 -> v2:
    * Add commit message with some rationale.

 hw/net/vmxnet3.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Am 25.08.22 um 11:29 schrieb Fiona Ebner:
> Currently, VMXNET3_MAX_MTU itself (being 9000) is not considered a
> valid value for the MTU, but a guest running ESXi 7.0 might try to
> set it and fail the assert [0].
> 
> In the Linux kernel, dev->max_mtu itself is a valid value for the MTU
> and for the vmxnet3 driver it's 9000, so a guest running Linux will
> also fail the assert when trying to set an MTU of 9000.
> 
> VMXNET3_MAX_MTU and s->mtu don't seem to be used in relation to buffer
> allocations/accesses, so allowing the upper limit itself as a value
> should be fine.
> 
> [0]: https://forum.proxmox.com/threads/114011/
> 
> Fixes: d05dcd94ae ("net: vmxnet3: validate configuration values during activate (CVE-2021-20203)")
> Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
> ---
> 
> Feel free to adapt the commit message as you see fit.
> 
> v1 -> v2:
>     * Add commit message with some rationale.
> 
>  hw/net/vmxnet3.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/hw/net/vmxnet3.c b/hw/net/vmxnet3.c
> index 0b7acf7f89..a2037583bf 100644
> --- a/hw/net/vmxnet3.c
> +++ b/hw/net/vmxnet3.c
> @@ -1441,7 +1441,7 @@ static void vmxnet3_activate_device(VMXNET3State *s)
>      vmxnet3_setup_rx_filtering(s);
>      /* Cache fields from shared memory */
>      s->mtu = VMXNET3_READ_DRV_SHARED32(d, s->drv_shmem, devRead.misc.mtu);
> -    assert(VMXNET3_MIN_MTU <= s->mtu && s->mtu < VMXNET3_MAX_MTU);
> +    assert(VMXNET3_MIN_MTU <= s->mtu && s->mtu <= VMXNET3_MAX_MTU);
>      VMW_CFPRN("MTU is %u", s->mtu);
>  
>      s->max_rx_frags =

Ping

On Wed, Dec 14, 2022 at 5:43 PM Fiona Ebner <f.ebner@proxmox.com> wrote:
>
> Am 25.08.22 um 11:29 schrieb Fiona Ebner:
> > Currently, VMXNET3_MAX_MTU itself (being 9000) is not considered a
> > valid value for the MTU, but a guest running ESXi 7.0 might try to
> > set it and fail the assert [0].
> >
> > In the Linux kernel, dev->max_mtu itself is a valid value for the MTU
> > and for the vmxnet3 driver it's 9000, so a guest running Linux will
> > also fail the assert when trying to set an MTU of 9000.
> >
> > VMXNET3_MAX_MTU and s->mtu don't seem to be used in relation to buffer
> > allocations/accesses, so allowing the upper limit itself as a value
> > should be fine.
> >
> > [0]: https://forum.proxmox.com/threads/114011/
> >
> > Fixes: d05dcd94ae ("net: vmxnet3: validate configuration values during activate (CVE-2021-20203)")
> > Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
> > ---
> >
> > Feel free to adapt the commit message as you see fit.
> >
> > v1 -> v2:
> >     * Add commit message with some rationale.
> >
> >  hw/net/vmxnet3.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/hw/net/vmxnet3.c b/hw/net/vmxnet3.c
> > index 0b7acf7f89..a2037583bf 100644
> > --- a/hw/net/vmxnet3.c
> > +++ b/hw/net/vmxnet3.c
> > @@ -1441,7 +1441,7 @@ static void vmxnet3_activate_device(VMXNET3State *s)
> >      vmxnet3_setup_rx_filtering(s);
> >      /* Cache fields from shared memory */
> >      s->mtu = VMXNET3_READ_DRV_SHARED32(d, s->drv_shmem, devRead.misc.mtu);
> > -    assert(VMXNET3_MIN_MTU <= s->mtu && s->mtu < VMXNET3_MAX_MTU);
> > +    assert(VMXNET3_MIN_MTU <= s->mtu && s->mtu <= VMXNET3_MAX_MTU);
> >      VMW_CFPRN("MTU is %u", s->mtu);
> >
> >      s->max_rx_frags =
>
> Ping

I've queued this patch.

Thanks

>