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charset="UTF-8" Sender: linux-serial-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org On Wed, Aug 5, 2020 at 6:26 PM Greg Kroah-Hartman wrote: > > On Wed, Aug 05, 2020 at 12:09:34PM +0000, Vabhav Sharma (OSS) wrote: > > > > > > > -----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; 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 > > > > > > 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 = (DMA_RX_TIMEOUT * baud / bits / > > > 1000) * 2; > > > > - sport->rx_dma_rng_buf_len = (1 << (fls(sport->rx_dma_rng_buf_len) > > > - 1)); > > > > + if (sport->rx_dma_rng_buf_len != 0) > > > > > > How can this variable become 0? > > Condition x, taking false branch > > Explicitly returning zero > > > > static __always_inline int fls(unsigned int x) > > { > > return x ? sizeof(x) * 8 - __builtin_clz(x) : 0; > > } > > What false branch? I'm assuming he's talking about the value after : in the ? operator. I am checking for the wrong thing in the if statement. We will have to check for the return value of fls() before performing the shift. I can change it and send a v3 if you agree. Please let me know. thanks, karthik