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Mon, 09 Mar 2026 09:31:04 -0700 (PDT) Message-ID: <2c72671a2195d019de38498e7cfcf19fab004267.camel@gmail.com> Subject: Re: [PATCH 3/3] iio: imu: bmi160: Remove potential undefined behavior in bmi160_config_pin() From: Nuno =?ISO-8859-1?Q?S=E1?= To: Josh Poimboeuf Cc: x86@kernel.org, linux-kernel@vger.kernel.org, Arnd Bergmann , Peter Zijlstra , Nathan Chancellor , Jonathan Cameron , David Lechner , Nuno =?ISO-8859-1?Q?S=E1?= , Andy Shevchenko Date: Mon, 09 Mar 2026 16:31:49 +0000 In-Reply-To: <4hgub636iyi4n62tnxn3b2ntxql4u5cznrn6loofgr5dpcwq3x@zmx4kxuyqix3> References: <84155f1de72b88d2841b16db97f47ffa4b0f747e.1773071992.git.jpoimboe@kernel.org> <4hgub636iyi4n62tnxn3b2ntxql4u5cznrn6loofgr5dpcwq3x@zmx4kxuyqix3> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.58.3 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Mon, 2026-03-09 at 09:27 -0700, Josh Poimboeuf wrote: > On Mon, Mar 09, 2026 at 04:16:16PM +0000, Nuno S=C3=A1 wrote: > > On Mon, 2026-03-09 at 09:03 -0700, Josh Poimboeuf wrote: > > > If 'pin' is not one of its expected values, the value of > > > 'int_out_ctrl_shift' is undefined.=C2=A0 With UBSAN enabled, this cau= ses > > > Clang to generate undefined behavior, resulting in the following > > > warning: > > >=20 > > > =C2=A0 drivers/iio/imu/bmi160/bmi160_core.o: warning: objtool: bmi160= _setup_irq() falls through to > > > next > > > function __cfi_bmi160_core_runtime_resume() > > >=20 > > > Prevent the UB and improve error handling by adding a BUG() if 'pin' = has > > > an unexpected value. > > >=20 > > > Cc: Jonathan Cameron > > > Cc: David Lechner > > > CC: Nuno S=C3=A1 > > > Cc: Andy Shevchenko > > > Fixes: 895bf81e6bbf ("iio:bmi160: add drdy interrupt support") > > > Reported-by: Arnd Bergmann > > > Closes: https://lore.kernel.org/a426d669-58bb-4be1-9eaa-6f3d83109e2d@= app.fastmail.com > > > Signed-off-by: Josh Poimboeuf > > > --- > > > =C2=A0drivers/iio/imu/bmi160/bmi160_core.c | 2 ++ > > > =C2=A01 file changed, 2 insertions(+) > > >=20 > > > diff --git a/drivers/iio/imu/bmi160/bmi160_core.c b/drivers/iio/imu/b= mi160/bmi160_core.c > > > index 5f47708b4c5d..e5326df75e49 100644 > > > --- a/drivers/iio/imu/bmi160/bmi160_core.c > > > +++ b/drivers/iio/imu/bmi160/bmi160_core.c > > > @@ -579,6 +579,8 @@ static int bmi160_config_pin(struct regmap *regma= p, enum bmi160_int_pin > > > pin, > > > =C2=A0 int_latch_mask =3D BMI160_INT2_LATCH_MASK; > > > =C2=A0 int_map_mask =3D BMI160_INT2_MAP_DRDY_EN; > > > =C2=A0 break; > > > + default: > > > + BUG(); > > > =C2=A0 } > > > =C2=A0 int_out_ctrl_mask =3D BMI160_INT_OUT_CTRL_MASK << int_out_ctrl= _shift; > > > =C2=A0 > >=20 > > AFAIK, BUG() is not something we should use lightly so I wonder why hav= ing it rather that a > > normal > > 'return -EINVAL'? > >=20 > > At the very least, it could be WARN but I still think that's too much f= or a device .probe(). Any > > special reason using BUG()? >=20 > Using BUG() for a default "invalid enum" is a common pattern, but indeed > returning an error would also be valid here.=C2=A0 I can change that to > return -EINVAL. >=20 > > Also seems like: > >=20 > > https://elixir.bootlin.com/linux/v7.0-rc2/source/drivers/iio/imu/bmi160= /bmi160_core.c#L624 > >=20 > > could be improved? Like setting 'pin_name' in the first switch() case. >=20 > Yeah, I assume you mean setting 'pin_name' to something like "invalid" > for the default case? Nope, I meant not duplicating the switch() case. The default should return = an error so I would say no need to bother in setting the name for that case. - Nuno S=C3=A1