Re: [PATCH] hw/net/vmxnet3: Fix guest-triggerable assert()

[Philippe Mathieu-Daudé]

Hi Thomas,

On 17/8/23 14:56, Thomas Huth wrote:
> The assert() that checks for valid MTU sizes can be triggered by
> the guest (e.g. with the reproducer code from the bug ticket
> https://gitlab.com/qemu-project/qemu/-/issues/517 ). Let's avoid
> this problem by simply logging the error and refusing to activate
> the device instead.
>
> Fixes: d05dcd94ae ("net: vmxnet3: validate configuration values during 
> activate")
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>   hw/net/vmxnet3.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/hw/net/vmxnet3.c b/hw/net/vmxnet3.c
> index 5dfacb1098..6674122a7e 100644
> --- a/hw/net/vmxnet3.c
> +++ b/hw/net/vmxnet3.c
> @@ -1439,7 +1439,10 @@ 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);
> +    if (s->mtu < VMXNET3_MIN_MTU || s->mtu > VMXNET3_MAX_MTU) {
> +        qemu_log_mask(LOG_GUEST_ERROR, "vmxnet3: Bad MTU size: %d\n", s->mtu);

mtu is uint32_t, otherwise:

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>

> +        return;
> +    }
>       VMW_CFPRN("MTU is %u", s->mtu);
>   
>       s->max_rx_frags =