Re: [PATCH] ALSA: core: fix buffer overflow in test_format_fill_silence()

[Ivan Orlov]

On 2/16/24 13:00, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@xxxxxxxx>
>
> KASAN caught a buffer overflow with the hardcoded 2048 byte buffer
> size, when 2080 bytes are written to it:
>
>   BUG: KASAN: slab-out-of-bounds in snd_pcm_format_set_silence+0x3bc/0x3e4
>   Write of size 8 at addr ffff0000c8149800 by task kunit_try_catch/1297
>
>   CPU: 0 PID: 1297 Comm: kunit_try_catch Tainted: G N 6.8.0-rc4-next-20240216 #1
>   Hardware name: linux,dummy-virt (DT)
>   Call trace:
>    kasan_report+0x78/0xc0
>    __asan_report_store_n_noabort+0x1c/0x28
>    snd_pcm_format_set_silence+0x3bc/0x3e4
>    _test_fill_silence+0xdc/0x298
>    test_format_fill_silence+0x110/0x228
>    kunit_try_run_case+0x144/0x3bc
>    kunit_generic_run_threadfn_adapter+0x50/0x94
>    kthread+0x330/0x3e8
>    ret_from_fork+0x10/0x20
>
>   Allocated by task 1297:
>    __kmalloc+0x17c/0x2f0
>    kunit_kmalloc_array+0x2c/0x78
>    test_format_fill_silence+0xcc/0x228
>    kunit_try_run_case+0x144/0x3bc
>    kunit_generic_run_threadfn_adapter+0x50/0x94
>    kthread+0x330/0x3e8
>    ret_from_fork+0x10/0x20
>
> Replace the incorrect size with the correct length of 260 64-bit samples.
>
> Reported-by: Naresh Kamboju <naresh.kamboju@xxxxxxxxxx>
> Fixes: 3e39acf56ede ("ALSA: core: Add sound core KUnit test")
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> ---
> Naresh, I slightly changed the patch to make the computation more obvious,
> can you test again to make sure I got this right?
> ---
>   sound/core/sound_kunit.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/sound/core/sound_kunit.c b/sound/core/sound_kunit.c
> index 5d5a7bf88de4..7f16101ece7a 100644
> --- a/sound/core/sound_kunit.c
> +++ b/sound/core/sound_kunit.c
> @@ -8,7 +8,7 @@
>   #include <sound/core.h>
>   #include <sound/pcm.h>
>   
> -#define SILENCE_BUFFER_SIZE 2048
> +#define SILENCE_BUFFER_SIZE (sizeof(u64) * 260)

I believe it would be good to define FILL_SILENCE_MAX_FRAMES to 260, 
update the 'buf_samples' array correspondingly and define the 
SILENCE_BUFFER_SIZE as (sizeof(u64) * FILL_SILENCE_MAX_FRAMES), so it 
would be more clear where '260' came from.

Thank you for fixing this!
--
Kind regards,
Ivan Orlov