Re: [alsa-devel] [PATCH] ASoC: Fix UBSAN warning at snd_soc_get/put_volsw_sx()

[Rohit Kumar]

Thanks Takashi for reviewing.


On 9/10/2018 11:56 PM, Takashi Iwai wrote:
> 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@xxxxxxxxxxxxxx>
> > ---
> >   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;

Yes, let me just update it.
> 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.
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Thanks,
Rohit