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Wed, 5 Aug 2020 12:09:34 +0000 Received: from VI1PR04MB4800.eurprd04.prod.outlook.com ([fe80::1c58:aed8:bd10:6c9e]) by VI1PR04MB4800.eurprd04.prod.outlook.com ([fe80::1c58:aed8:bd10:6c9e%3]) with mapi id 15.20.3239.022; Wed, 5 Aug 2020 12:09:34 +0000 From: "Vabhav Sharma (OSS)" To: Greg Kroah-Hartman , B K Karthik CC: Jiri Slaby , "linux-serial@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "Vabhav Sharma (OSS)" , "bhuvanchandra.dv@toradex.com" Subject: RE: [PATCH v2] tty: serial: fsl_lpuart.c: prevent a bad shift operation Thread-Topic: [PATCH v2] tty: serial: fsl_lpuart.c: prevent a bad shift operation Thread-Index: AQHWayFI3yg/bZUvNkSlmfbzKR6GJg== Date: Wed, 5 Aug 2020 12:09:34 +0000 Message-ID: References: <20200721174228.misj2mgqzcfz2lsj@pesu.pes.edu> <20200729160333.GA3652767@kroah.com> In-Reply-To: <20200729160333.GA3652767@kroah.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: linuxfoundation.org; dkim=none (message not signed) header.d=none;linuxfoundation.org; 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x-ms-exchange-antispam-messagedata: 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 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: oss.nxp.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: VI1PR04MB4800.eurprd04.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: af13b12b-cd4a-4ec6-6689-08d839386aa6 X-MS-Exchange-CrossTenant-originalarrivaltime: 05 Aug 2020 12:09:34.2017 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 686ea1d3-bc2b-4c6f-a92c-d99c5c301635 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: 7C9GCJNILBD0WEXhjHwVjyFRyoY9XoUnVgnEFpBUJ0O7jF9v+tLDo+u05imw2AX+6s0zxjwWPneWBuvTHMpZaQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: VI1PR04MB6974 Sender: linux-serial-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org > -----Original Message----- > From: Greg Kroah-Hartman > Sent: Wednesday, July 29, 2020 9:34 PM > To: B K Karthik > Cc: Jiri Slaby ; linux-serial@vger.kernel.org; linu= x- > kernel@vger.kernel.org; Vabhav Sharma (OSS) > ; bhuvanchandra.dv@toradex.com > Subject: Re: [PATCH v2] tty: serial: fsl_lpuart.c: prevent a bad shift op= eration >=20 > On Tue, Jul 21, 2020 at 11:12:29PM +0530, B K Karthik wrote: > > prevent a bad shift operation by verifying that the argument to fls is > > non zero. > > > > Reported-by: "Vabhav Sharma (OSS)" > > Signed-off-by: B K Karthik > > --- > > v1 -> v2: > > added Reported-by tag > > > > drivers/tty/serial/fsl_lpuart.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/tty/serial/fsl_lpuart.c > > b/drivers/tty/serial/fsl_lpuart.c index 7ca642249224..0cc64279cd2d > > 100644 > > --- a/drivers/tty/serial/fsl_lpuart.c > > +++ b/drivers/tty/serial/fsl_lpuart.c > > @@ -1168,7 +1168,8 @@ static inline int lpuart_start_rx_dma(struct > lpuart_port *sport) > > * 10ms at any baud rate. > > */ > > sport->rx_dma_rng_buf_len =3D (DMA_RX_TIMEOUT * baud / bits / > 1000) * 2; > > - sport->rx_dma_rng_buf_len =3D (1 << (fls(sport->rx_dma_rng_buf_len) > - 1)); > > + if (sport->rx_dma_rng_buf_len !=3D 0) >=20 > How can this variable become 0? Condition x, taking false branch Explicitly returning zero=20 static __always_inline int fls(unsigned int x) { return x ? sizeof(x) * 8 - __builtin_clz(x) : 0; } >=20 > thanks, >=20 > greg k-h