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To: Jonathan Cameron , , CC: Jonathan Cameron , Lars-Peter Clausen References: <20200517173000.220819-1-jic23@kernel.org> <20200517173000.220819-8-jic23@kernel.org> <951a305b-b3b4-6cfc-f39a-f7458dfcb54b@ti.com> <83B13776-904F-4FCF-93A6-D430281E4B55@jic23.retrosnub.co.uk> From: "Andrew F. Davis" Message-ID: Date: Thu, 21 May 2020 09:11:10 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <83B13776-904F-4FCF-93A6-D430281E4B55@jic23.retrosnub.co.uk> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-EXCLAIMER-MD-CONFIG: e1e8a2fd-e40a-4ac6-ac9b-f7e9cc9ee180 Sender: linux-iio-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-iio@vger.kernel.org On 5/18/20 12:06 PM, Jonathan Cameron wrote: > > > On 18 May 2020 01:09:47 BST, "Andrew F. Davis" wrote: >> On 5/17/20 1:29 PM, jic23@kernel.org wrote: >>> From: Jonathan Cameron >>> >>> One of a class of bugs pointed out by Lars in a recent review. >>> iio_push_to_buffers_with_timestamp assumes the buffer used is aligned >>> to the size of the timestamp (8 bytes). This is not guaranteed in >>> this driver which uses a 32 byte array of smaller elements on the >> stack. >>> As Lars also noted this anti pattern can involve a leak of data to >>> userspace and that indeed can happen here. We close both issues by >>> moving to a suitable structure in the iio_priv() data with alignment >>> explicitly requested. This data is allocated with kzalloc so no >>> data can leak appart from previous readings. >>> >>> Fixes: eec96d1e2d31 ("iio: health: Add driver for the TI AFE4403 >> heart monitor") >>> Reported-by: Lars-Peter Clausen >>> Signed-off-by: Jonathan Cameron >>> Cc: Andrew F. Davis >>> --- >>> drivers/iio/health/afe4403.c | 9 ++++++--- >>> 1 file changed, 6 insertions(+), 3 deletions(-) >>> >>> diff --git a/drivers/iio/health/afe4403.c >> b/drivers/iio/health/afe4403.c >>> index e9f87e42ff4f..a3507624b30f 100644 >>> --- a/drivers/iio/health/afe4403.c >>> +++ b/drivers/iio/health/afe4403.c >>> @@ -65,6 +65,7 @@ static const struct reg_field afe4403_reg_fields[] >> = { >>> * @regulator: Pointer to the regulator for the IC >>> * @trig: IIO trigger for this device >>> * @irq: ADC_RDY line interrupt number >>> + * @buffer: Used to construct data layout to push into IIO buffer. >>> */ >>> struct afe4403_data { >>> struct device *dev; >>> @@ -74,6 +75,8 @@ struct afe4403_data { >>> struct regulator *regulator; >>> struct iio_trigger *trig; >>> int irq; >>> + /* Ensure suitable alignment for timestamp */ >>> + s32 buffer[8] __aligned(8); >> >> >> One of those fancy structs with the timestamp specified would be nice >> here like the other patches. IIRC we have 6 s32 channels, plus a s64 >> ts. > > I think we may only have some of those channels enabled. So ts may be it several > locations in the buffer. > Might have been better to have the ts at the beginning, could have also helped with alignment for when an odd number of channels are enabled. > Hence we could use the structure approach but it might give a false sense > of what is going on. > That's true, it can always be cleaned later then. Andrew > J >> >> Other than that everything looks good. >> >> Andrew >> >> >>> }; >>> >>> enum afe4403_chan_id { >>> @@ -309,7 +312,6 @@ static irqreturn_t afe4403_trigger_handler(int >> irq, void *private) >>> struct iio_dev *indio_dev = pf->indio_dev; >>> struct afe4403_data *afe = iio_priv(indio_dev); >>> int ret, bit, i = 0; >>> - s32 buffer[8]; >>> u8 tx[4] = {AFE440X_CONTROL0, 0x0, 0x0, AFE440X_CONTROL0_READ}; >>> u8 rx[3]; >>> >>> @@ -326,7 +328,7 @@ static irqreturn_t afe4403_trigger_handler(int >> irq, void *private) >>> if (ret) >>> goto err; >>> >>> - buffer[i++] = get_unaligned_be24(&rx[0]); >>> + afe->buffer[i++] = get_unaligned_be24(&rx[0]); >>> } >>> >>> /* Disable reading from the device */ >>> @@ -335,7 +337,8 @@ static irqreturn_t afe4403_trigger_handler(int >> irq, void *private) >>> if (ret) >>> goto err; >>> >>> - iio_push_to_buffers_with_timestamp(indio_dev, buffer, >> pf->timestamp); >>> + iio_push_to_buffers_with_timestamp(indio_dev, afe->buffer, >>> + pf->timestamp); >>> err: >>> iio_trigger_notify_done(indio_dev->trig); >>> >>> >