Re: [PULL v2 17/61] virtio-snd: check for invalid param shift operands

[Volker Rümelin]

Am 01.08.24 um 10:22 schrieb Michael S. Tsirkin:
> On Sat, Jul 27, 2024 at 08:55:10AM +0200, Volker Rümelin wrote:
>>> From: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
>>>
>>> When setting the parameters of a PCM stream, we compute the bit flag
>>> with the format and rate values as shift operand to check if they are
>>> set in supported_formats and supported_rates.
>>>
>>> If the guest provides a format/rate value which when shifting 1 results
>>> in a value bigger than the number of bits in
>>> supported_formats/supported_rates, we must report an error.
>>>
>>> Previously, this ended up triggering the not reached assertions later
>>> when converting to internal QEMU values.
>>>
>>> Reported-by: Zheyu Ma <zheyuma97@gmail.com>
>>> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2416
>>> Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
>>> Message-Id: <virtio-snd-fuzz-2416-fix-v1-manos.pitsidianakis@linaro.org>
>>> Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
>>> Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
>>> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
>>> ---
>>>  hw/audio/virtio-snd.c | 6 ++++--
>>>  1 file changed, 4 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/hw/audio/virtio-snd.c b/hw/audio/virtio-snd.c
>>> index e6432ac959..e5196aa4bb 100644
>>> --- a/hw/audio/virtio-snd.c
>>> +++ b/hw/audio/virtio-snd.c
>>> @@ -282,11 +282,13 @@ uint32_t virtio_snd_set_pcm_params(VirtIOSound *s,
>>>          error_report("Number of channels is not supported.");
>>>          return cpu_to_le32(VIRTIO_SND_S_NOT_SUPP);
>>>      }
>>> -    if (!(supported_formats & BIT(params->format))) {
>> Hi Manos,
>>
>> this patch doesn't work as intended. I guess you wanted to write
>>
>>     if (params->format >= sizeof(supported_formats) * BITS_PER_BYTE ||
>>         !(supported_formats & BIT(params->format))) {
>>
>>> +    if (BIT(params->format) > sizeof(supported_formats) ||
>>> +        !(supported_formats & BIT(params->format))) {
>>>          error_report("Stream format is not supported.");
>>>          return cpu_to_le32(VIRTIO_SND_S_NOT_SUPP);
>>>      }
>>> -    if (!(supported_rates & BIT(params->rate))) {
>>     if (params->rate >= sizeof(supported_rates) * BITS_PER_BYTE ||
>>         !(supported_rates & BIT(params->rate))) {
>>
>> With best regards,
>> Volker
>
> Any response here? Should I revert?

No response so far. It's not necessary to revert. I'll send a patch.

With best regards,
Volker

>>> +    if (BIT(params->rate) > sizeof(supported_rates) ||
>>> +        !(supported_rates & BIT(params->rate))) {
>>>          error_report("Stream rate is not supported.");
>>>          return cpu_to_le32(VIRTIO_SND_S_NOT_SUPP);
>>>      }