linux-kernel - Re: [PATCH] ASoC: Fix UBSAN warning at snd_soc_get/put_volsw

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Date:   Mon, 10 Sep 2018 20:26:18 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     "Rohit kumar" <rohitkr@...eaurora.org>
Cc:     <alsa-devel@...a-project.org>, <lgirdwood@...il.com>,
        <broonie@...nel.org>, <perex@...ex.cz>,
        <rohkumar@....qualcomm.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ASoC: Fix UBSAN warning at snd_soc_get/put_volsw_sx()

On Mon, 10 Sep 2018 19:33:56 +0200,
Rohit kumar wrote:
> 
> In functions snd_soc_get_volsw_sx() or snd_soc_put_volsw_sx(),
> if the result of (min + max) is negative, then fls() returns
> signed integer with value as 32. This leads to signed integer
> overflow as complete operation is considered as signed integer.
> 
> UBSAN: Undefined behaviour in sound/soc/soc-ops.c:382:50
> signed integer overflow:
> -2147483648 - 1 cannot be represented in type 'int'
> Call trace:
> [<ffffff852f746fe4>] __dump_stack lib/dump_stack.c:15 [inline]
> [<ffffff852f746fe4>] dump_stack+0xec/0x158 lib/dump_stack.c:51
> [<ffffff852f7b5f3c>] ubsan_epilogue+0x18/0x50 lib/ubsan.c:164
> [<ffffff852f7b6840>] handle_overflow+0xf8/0x130 lib/ubsan.c:195
> [<ffffff852f7b68f0>] __ubsan_handle_sub_overflow+0x34/0x44 lib/ubsan.c:211
> [<ffffff85307971a0>] snd_soc_get_volsw_sx+0x1a8/0x1f8 sound/soc/soc-ops.c:382
> 
> Typecast the operation to unsigned int to fix the issue.
> 
> Signed-off-by: Rohit kumar <rohitkr@...eaurora.org>
> ---
>  sound/soc/soc-ops.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/sound/soc/soc-ops.c b/sound/soc/soc-ops.c
> index 592efb3..f8e3190 100644
> --- a/sound/soc/soc-ops.c
> +++ b/sound/soc/soc-ops.c
> @@ -373,7 +373,7 @@ int snd_soc_get_volsw_sx(struct snd_kcontrol *kcontrol,
>  	unsigned int rshift = mc->rshift;
>  	int max = mc->max;
>  	int min = mc->min;
> -	unsigned int mask = (1 << (fls(min + max) - 1)) - 1;
> +	unsigned int mask = ((unsigned int)(1 << (fls(min + max) - 1)) - 1);

Cat it be simpler like below instead?
	unsigned int mask = (1U << (fls(min + max) - 1)) - 1;


thanks,

Takashi

>  	unsigned int val;
>  	int ret;
>  
> @@ -418,7 +418,7 @@ int snd_soc_put_volsw_sx(struct snd_kcontrol *kcontrol,
>  	unsigned int rshift = mc->rshift;
>  	int max = mc->max;
>  	int min = mc->min;
> -	unsigned int mask = (1 << (fls(min + max) - 1)) - 1;
> +	unsigned int mask = ((unsigned int)(1 << (fls(min + max) - 1)) - 1);
>  	int err = 0;
>  	unsigned int val, val_mask, val2 = 0;
>  
> -- 
> Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc.,
> is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.
> 
>