On Tue, Mar 14, 2023 at 10:12 PM Linus Walleij <linus.walleij@xxxxxxxxxx> wrote:
> On Tue, Mar 14, 2023 at 8:37 PM Kasumov Ruslan <xhxgldhlpfy@xxxxxxxxx> wrote:
>
> > The left side of the loop condition never becomes false.
> > hwchan cannot be NULL, because it points to elements of the
> > hw_channels array that takes one of 4 predefined values:
> > pm8018_xoadc_channels, pm8038_xoadc_channels,
> > pm8058_xoadc_channels, pm8921_xoadc_channels.
> >
> > Found by Linux Verification Center (linuxtesting.org) with SVACE.
>
> I am not impressed with that tool. See below:
>
> > Fixes: 63c3ecd946d4 ("iio: adc: add a driver for Qualcomm PM8xxx HK/XOADC")
> > Signed-off-by: Kasumov Ruslan <s02210418@xxxxxxxxxxxxx>
>
> (...)
> > hwchan = &hw_channels[0];
> > - while (hwchan && hwchan->datasheet_name) {
> > + while (hwchan->datasheet_name) {
> > if (hwchan->pre_scale_mux == pre_scale_mux &&
> > hwchan->amux_channel == amux_channel)
> > break;
>
> NAK have you tested this on a real system?
>
> Here is the complete loop:
>
> hwchan = &hw_channels[0];
> while (hwchan && hwchan->datasheet_name) {
> if (hwchan->pre_scale_mux == pre_scale_mux &&
> hwchan->amux_channel == amux_channel)
> break;
> hwchan++;
> chid++;
> }
>
> Notice how hwchan is used as iterator in hwchan++.
>
> What you are doing will cause a zero-pointer dereference.
Nah the AI is smarter than me this time, I'm wrong, I think :(
hwchan is indeed never NULL here, and the code immediately
after unconditionally dereferences hwchan->datasheet_name.
Who wrote this convoluted code again:
63c3ecd946d4a (Linus Walleij 2017-04-04 14:08:19 +0200 759)
chid = 0;
63c3ecd946d4a (Linus Walleij 2017-04-04 14:08:19 +0200 760)
hwchan = &hw_channels[0];
63c3ecd946d4a (Linus Walleij 2017-04-04 14:08:19 +0200 761)
while (hwchan && hwchan->datasheet_name) {
63c3ecd946d4a (Linus Walleij 2017-04-04 14:08:19 +0200 762)
if (hwchan->pre_scale_mux == pre_scale_mux &&
63c3ecd946d4a (Linus Walleij 2017-04-04 14:08:19 +0200 763)
hwchan->amux_channel == amux_channel)
63c3ecd946d4a (Linus Walleij 2017-04-04 14:08:19 +0200 764)
break;
63c3ecd946d4a (Linus Walleij 2017-04-04 14:08:19 +0200 765)
hwchan++;
63c3ecd946d4a (Linus Walleij 2017-04-04 14:08:19 +0200 766)
chid++;
63c3ecd946d4a (Linus Walleij 2017-04-04 14:08:19 +0200 767) }
63c3ecd946d4a (Linus Walleij 2017-04-04 14:08:19 +0200 768)
/* The sentinel does not have a name assigned */
63c3ecd946d4a (Linus Walleij 2017-04-04 14:08:19 +0200 769)
if (!hwchan->datasheet_name) {
Oh that guy ...
I wonder if we can make it look better and less unintuitive.
Yours,
Linus Walleij
