Re: [PATCH] hw/audio/sb16: Avoid assertion by restricting I/O sampling rate range

[Philippe Mathieu-Daudé]

On 6/14/21 2:11 PM, Qiang Liu wrote:
> Hi Phil,
> 
> Thanks for inviting me. I've applied your patch. It seems fine
> because my sb16 fuzzer is running for another 24 hours and
> it has no crash yet.

Thanks for testing!

Can we use your "Tested-by: Qiang Liu <cyruscyliu@gmail.com>" tag?

> I can also double-check the specification.

If you do, please send a "Reviewed-by: Qiang Liu <cyruscyliu@gmail.com>"
tag :)

> Best,
> Qiang
> 
> On Mon, Jun 14, 2021 at 7:13 PM Philippe Mathieu-Daudé <f4bug@amsat.org> 
> wrote:
>>
>> ping?
>>
>> On 6/1/21 5:18 PM, Philippe Mathieu-Daudé wrote:
>>> While the SB16 seems to work up to 48000 Hz, the "Sound Blaster Series
>>> Hardware Programming Guide" limit the sampling range from 4000 Hz to
>>> 44100 Hz (Section 3-9, 3-10: Digitized Sound I/O Programming, tables
>>> 3-2 and 3-3).
>>>
>>> Later, section 6-15 (DSP Commands) is more specific regarding the 41h /
>>> 42h registers (Set digitized sound output sampling rate):
>>>
>>>   Valid sampling rates range from 5000 to 45000 Hz inclusive.
>>>
>>> There is no comment regarding error handling if the register is filled
>>> with an out-of-range value.  (See also section 3-28 "8-bit or 16-bit
>>> Auto-initialize Transfer"). Assume limits are enforced in hardware.
>>>
>>> This fixes triggering an assertion in audio_calloc():
>>>
>>>   #1 abort
>>>   #2 audio_bug audio/audio.c:119:9
>>>   #3 audio_calloc audio/audio.c:154:9
>>>   #4 audio_pcm_sw_alloc_resources_out audio/audio_template.h:116:15
>>>   #5 audio_pcm_sw_init_out audio/audio_template.h:175:11
>>>   #6 audio_pcm_create_voice_pair_out audio/audio_template.h:410:9
>>>   #7 AUD_open_out audio/audio_template.h:503:14
>>>   #8 continue_dma8 hw/audio/sb16.c:216:20
>>>   #9 dma_cmd8 hw/audio/sb16.c:276:5
>>>   #10 command hw/audio/sb16.c:0
>>>   #11 dsp_write hw/audio/sb16.c:949:13
>>>   #12 portio_write softmmu/ioport.c:205:13
>>>   #13 memory_region_write_accessor softmmu/memory.c:491:5
>>>   #14 access_with_adjusted_size softmmu/memory.c:552:18
>>>   #15 memory_region_dispatch_write softmmu/memory.c:0:13
>>>   #16 flatview_write_continue softmmu/physmem.c:2759:23
>>>   #17 flatview_write softmmu/physmem.c:2799:14
>>>   #18 address_space_write softmmu/physmem.c:2891:18
>>>   #19 cpu_outw softmmu/ioport.c:70:5
>>>
>>> [*] http://www.baudline.com/solutions/full_duplex/sb16_pci/index.html
>>>
>>> Fixes: 85571bc7415 ("audio merge (malc)")
>>> Buglink: https://bugs.launchpad.net/bugs/1910603
>>> OSS-Fuzz Report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=29174
>>> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
>>> ---
>>>  hw/audio/sb16.c              | 14 ++++++++++
>>>  tests/qtest/fuzz-sb16-test.c | 52 ++++++++++++++++++++++++++++++++++++
>>>  MAINTAINERS                  |  1 +
>>>  tests/qtest/meson.build      |  1 +
>>>  4 files changed, 68 insertions(+)
>>>  create mode 100644 tests/qtest/fuzz-sb16-test.c
>>>
>>> diff --git a/hw/audio/sb16.c b/hw/audio/sb16.c
>>> index 8b207004102..5cf121fe363 100644
>>> --- a/hw/audio/sb16.c
>>> +++ b/hw/audio/sb16.c
>>> @@ -115,6 +115,9 @@ struct SB16State {
>>>      PortioList portio_list;
>>>  };
>>>
>>> +#define SAMPLE_RATE_MIN 5000
>>> +#define SAMPLE_RATE_MAX 45000
>>> +
>>>  static void SB_audio_callback (void *opaque, int free);
>>>
>>>  static int magic_of_irq (int irq)
>>> @@ -241,6 +244,17 @@ static void dma_cmd8 (SB16State *s, int mask, int 
>>> dma_len)
>>>          int tmp = (256 - s->time_const);
>>>          s->freq = (1000000 + (tmp / 2)) / tmp;
>>>      }
>>> +    if (s->freq < SAMPLE_RATE_MIN) {
>>> +        qemu_log_mask(LOG_GUEST_ERROR,
>>> +                      "sampling range too low: %d, increasing to %u\n",
>>> +                      s->freq, SAMPLE_RATE_MIN);
>>> +        s->freq = SAMPLE_RATE_MIN;
>>> +    } else if (s->freq > SAMPLE_RATE_MAX) {
>>> +        qemu_log_mask(LOG_GUEST_ERROR,
>>> +                      "sampling range too high: %d, decreasing to %u\n",
>>> +                      s->freq, SAMPLE_RATE_MAX);
>>> +        s->freq = SAMPLE_RATE_MAX;
>>> +    }
>>>
>>>      if (dma_len != -1) {
>>>          s->block_size = dma_len << s->fmt_stereo;
>>> diff --git a/tests/qtest/fuzz-sb16-test.c b/tests/qtest/fuzz-sb16-test.c
>>> new file mode 100644
>>> index 00000000000..51030cd7dc4
>>> --- /dev/null
>>> +++ b/tests/qtest/fuzz-sb16-test.c
>>> @@ -0,0 +1,52 @@
>>> +/*
>>> + * QTest fuzzer-generated testcase for sb16 audio device
>>> + *
>>> + * Copyright (c) 2021 Philippe Mathieu-Daudé <f4bug@amsat.org>
>>> + *
>>> + * SPDX-License-Identifier: GPL-2.0-or-later
>>> + */
>>> +
>>> +#include "qemu/osdep.h"
>>> +#include "libqos/libqtest.h"
>>> +
>>> +/*
>>> + * This used to trigger the assert in audio_calloc
>>> + * https://bugs.launchpad.net/qemu/+bug/1910603
>>> + */
>>> +static void test_fuzz_sb16_0x1c(void)
>>> +{
>>> +    QTestState *s = qtest_init("-M q35 -display none "
>>> +                               "-device sb16,audiodev=snd0 "
>>> +                               "-audiodev none,id=snd0");
>>> +    qtest_outw(s, 0x22c, 0x41);
>>> +    qtest_outb(s, 0x22c, 0x00);
>>> +    qtest_outw(s, 0x22c, 0x1004);
>>> +    qtest_outw(s, 0x22c, 0x001c);
>>> +    qtest_quit(s);
>>> +}
>>> +
>>> +static void test_fuzz_sb16_0x91(void)
>>> +{
>>> +    QTestState *s = qtest_init("-M pc -display none "
>>> +                               "-device sb16,audiodev=none "
>>> +                               "-audiodev id=none,driver=none");
>>> +    qtest_outw(s, 0x22c, 0xf141);
>>> +    qtest_outb(s, 0x22c, 0x00);
>>> +    qtest_outb(s, 0x22c, 0x24);
>>> +    qtest_outb(s, 0x22c, 0x91);
>>> +    qtest_quit(s);
>>> +}
>>> +
>>> +int main(int argc, char **argv)
>>> +{
>>> +    const char *arch = qtest_get_arch();
>>> +
>>> +    g_test_init(&argc, &argv, NULL);
>>> +
>>> +   if (strcmp(arch, "i386") == 0) {
>>> +        qtest_add_func("fuzz/test_fuzz_sb16/1c", test_fuzz_sb16_0x1c);
>>> +        qtest_add_func("fuzz/test_fuzz_sb16/91", test_fuzz_sb16_0x91);
>>> +   }
>>> +
>>> +   return g_test_run();
>>> +}
>>> diff --git a/MAINTAINERS b/MAINTAINERS
>>> index 5f55404f2fa..7edb26d2293 100644
>>> --- a/MAINTAINERS
>>> +++ b/MAINTAINERS
>>> @@ -2213,6 +2213,7 @@ F: qapi/audio.json
>>>  F: tests/qtest/ac97-test.c
>>>  F: tests/qtest/es1370-test.c
>>>  F: tests/qtest/intel-hda-test.c
>>> +F: tests/qtest/fuzz-sb16-test.c
>>>
>>>  Block layer core
>>>  M: Kevin Wolf <kwolf@redhat.com>
>>> diff --git a/tests/qtest/meson.build b/tests/qtest/meson.build
>>> index c3a223a83d6..b03e8541700 100644
>>> --- a/tests/qtest/meson.build
>>> +++ b/tests/qtest/meson.build
>>> @@ -20,6 +20,7 @@
>>>  qtests_generic = \
>>>    (config_all_devices.has_key('CONFIG_MEGASAS_SCSI_PCI') ? 
>>> ['fuzz-megasas-test'] : []) + \
>>>    (config_all_devices.has_key('CONFIG_VIRTIO_SCSI') ? 
>>> ['fuzz-virtio-scsi-test'] : []) + \
>>> +  (config_all_devices.has_key('CONFIG_SB16') ? ['fuzz-sb16-test'] : []) + \
>>>    [
>>>    'cdrom-test',
>>>    'device-introspect-test',
>>>
>