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Thu, 08 Jan 2026 01:19:10 -0800 (PST) Message-ID: Subject: Re: [PATCH v2] iio: dac: ad3552r-hs: fix out-of-bound write in ad3552r_hs_write_data_source From: Nuno =?ISO-8859-1?Q?S=E1?= To: Miaoqian Lin , Lars-Peter Clausen , Michael Hennerich , Jonathan Cameron , David Lechner , Nuno =?ISO-8859-1?Q?S=E1?= , Andy Shevchenko , Angelo Dureghello , linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org Cc: stable@vger.kernel.org Date: Thu, 08 Jan 2026 09:19:52 +0000 In-Reply-To: <20260107143550.34324-1-linmq006@gmail.com> References: <20260107143550.34324-1-linmq006@gmail.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.58.2 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Wed, 2026-01-07 at 22:35 +0800, Miaoqian Lin wrote: > When simple_write_to_buffer() succeeds, it returns the number of bytes > actually copied to the buffer. The code incorrectly uses 'count' > as the index for null termination instead of the actual bytes copied. > If count exceeds the buffer size, this leads to out-of-bounds write. > Add a check for the count and use the return value as the index. >=20 > The bug was validated using a demo module that mirrors the original > code and was tested under QEMU. >=20 > Pattern of the bug: > - A fixed 64-byte stack buffer is filled using count. > - If count > 64, the code still does buf[count] =3D '\0', causing an > - out-of-bounds write on the stack. >=20 > Steps for reproduce: > - Opens the device node. > - Writes 128 bytes of A to it. > - This overflows the 64-byte stack buffer and KASAN reports the OOB. >=20 > Found via static analysis. This is similar to the > commit da9374819eb3 ("iio: backend: fix out-of-bound write") >=20 > Fixes: b1c5d68ea66e ("iio: dac: ad3552r-hs: add support for internal ramp= ") > Cc: stable@vger.kernel.org > Signed-off-by: Miaoqian Lin > --- Reviewed-by: Nuno S=C3=A1 > changes in v2: > - update commit message > - v1 link: https://lore.kernel.org/all/20251027150713.59067-1-linmq006@gm= ail.com/ > --- > =C2=A0drivers/iio/dac/ad3552r-hs.c | 5 ++++- > =C2=A01 file changed, 4 insertions(+), 1 deletion(-) >=20 > diff --git a/drivers/iio/dac/ad3552r-hs.c b/drivers/iio/dac/ad3552r-hs.c > index 41b96b48ba98..a9578afa7015 100644 > --- a/drivers/iio/dac/ad3552r-hs.c > +++ b/drivers/iio/dac/ad3552r-hs.c > @@ -549,12 +549,15 @@ static ssize_t ad3552r_hs_write_data_source(struct = file *f, > =C2=A0 > =C2=A0 guard(mutex)(&st->lock); > =C2=A0 > + if (count >=3D sizeof(buf)) > + return -ENOSPC; > + > =C2=A0 ret =3D simple_write_to_buffer(buf, sizeof(buf) - 1, ppos, userbuf= , > =C2=A0 =C2=A0=C2=A0=C2=A0=C2=A0 count); > =C2=A0 if (ret < 0) > =C2=A0 return ret; > =C2=A0 > - buf[count] =3D '\0'; > + buf[ret] =3D '\0'; > =C2=A0 > =C2=A0 ret =3D match_string(dbgfs_attr_source, ARRAY_SIZE(dbgfs_attr_sour= ce), > =C2=A0 =C2=A0=C2=A0 buf);