linux-kernel - Re: [PATCH -next] ALSA: pcm: fix undefined behavior in bit shift for SNDRV_PCM_RATE

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Date:   Mon, 21 Nov 2022 11:35:03 +0100
From:   Takashi Iwai <tiwai@...e.de>
To:     Baisong Zhong <zhongbaisong@...wei.com>
Cc:     <linux-kernel@...r.kernel.org>, <alsa-devel@...a-project.org>,
        <perex@...ex.cz>, <tiwai@...e.com>, <broonie@...nel.org>,
        <kuninori.morimoto.gx@...esas.com>
Subject: Re: [PATCH -next] ALSA: pcm: fix undefined behavior in bit shift for SNDRV_PCM_RATE_KNOT

On Mon, 21 Nov 2022 03:33:29 +0100,
Baisong Zhong wrote:
> 
> Shifting signed 32-bit value by 31 bits is undefined, so changing
> significant bit to unsigned. The UBSAN warning calltrace like below:
> 
> UBSAN: shift-out-of-bounds in sound/core/pcm_native.c:2676:21
> left shift of 1 by 31 places cannot be represented in type 'int'
> ...
> Call Trace:
>  <TASK>
>  dump_stack_lvl+0x8d/0xcf
>  ubsan_epilogue+0xa/0x44
>  __ubsan_handle_shift_out_of_bounds+0x1e7/0x208
>  snd_pcm_open_substream+0x9f0/0xa90
>  snd_pcm_oss_open.part.26+0x313/0x670
>  snd_pcm_oss_open+0x30/0x40
>  soundcore_open+0x18b/0x2e0
>  chrdev_open+0xe2/0x270
>  do_dentry_open+0x2f7/0x620
>  path_openat+0xd66/0xe70
>  do_filp_open+0xe3/0x170
>  do_sys_openat2+0x357/0x4a0
>  do_sys_open+0x87/0xd0
>  do_syscall_64+0x34/0x80
> 
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Signed-off-by: Baisong Zhong <zhongbaisong@...wei.com>
> ---
>  include/sound/pcm.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/sound/pcm.h b/include/sound/pcm.h
> index 7b1a022910e8..ec28c2ec89de 100644
> --- a/include/sound/pcm.h
> +++ b/include/sound/pcm.h
> @@ -123,7 +123,7 @@ struct snd_pcm_ops {
>  #define SNDRV_PCM_RATE_384000		(1<<14)		/* 384000Hz */
>  
>  #define SNDRV_PCM_RATE_CONTINUOUS	(1<<30)		/* continuous range */
> -#define SNDRV_PCM_RATE_KNOT		(1<<31)		/* supports more non-continuos rates */
> +#define SNDRV_PCM_RATE_KNOT		(1U<<31)	/* supports more non-continuos rates */

Could you rather update all SNDRV_PCM_RATE_* to 1U?
Otherwise it'll look inconsistent.


thanks,

Takashi