This is a note to let you know that I've just added the patch titled
iio:magnetometer:ak8975 Fix alignment and data leak issues.
to my staging git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git in the staging-linus branch.
The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)
The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.
If you have any questions about this process, please let me know.
From 02ad21cefbac4d89ac443866f25b90449527737b Mon Sep 17 00:00:00 2001
From: Jonathan Cameron Jonathan.Cameron@huawei.com Date: Wed, 22 Jul 2020 16:50:49 +0100 Subject: iio:magnetometer:ak8975 Fix alignment and data leak issues.
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 an 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.
This data is allocated with kzalloc so no data can leak apart from previous readings.
The explicit alignment of ts is not necessary in this case as by coincidence the padding will end up the same, however I consider it to make the code less fragile and have included it.
Fixes: bc11ca4a0b84 ("iio:magnetometer:ak8975: triggered buffer support") Reported-by: Lars-Peter Clausen lars@metafoo.de Cc: Gregor Boirie gregor.boirie@parrot.com Cc: Linus Walleij linus.walleij@linaro.org Signed-off-by: Jonathan Cameron Jonathan.Cameron@huawei.com Reviewed-by: Andy Shevchenko andy.shevchenko@gmail.com Cc: Stable@vger.kernel.org --- drivers/iio/magnetometer/ak8975.c | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-)
diff --git a/drivers/iio/magnetometer/ak8975.c b/drivers/iio/magnetometer/ak8975.c index 03d71f796177..623766ff800b 100644 --- a/drivers/iio/magnetometer/ak8975.c +++ b/drivers/iio/magnetometer/ak8975.c @@ -366,6 +366,12 @@ struct ak8975_data { struct iio_mount_matrix orientation; struct regulator *vdd; struct regulator *vid; + + /* Ensure natural alignment of timestamp */ + struct { + s16 channels[3]; + s64 ts __aligned(8); + } scan; };
/* Enable attached power regulator if any. */ @@ -793,7 +799,6 @@ static void ak8975_fill_buffer(struct iio_dev *indio_dev) const struct i2c_client *client = data->client; const struct ak_def *def = data->def; int ret; - s16 buff[8]; /* 3 x 16 bits axis values + 1 aligned 64 bits timestamp */ __le16 fval[3];
mutex_lock(&data->lock); @@ -816,12 +821,13 @@ static void ak8975_fill_buffer(struct iio_dev *indio_dev) mutex_unlock(&data->lock);
/* Clamp to valid range. */ - buff[0] = clamp_t(s16, le16_to_cpu(fval[0]), -def->range, def->range); - buff[1] = clamp_t(s16, le16_to_cpu(fval[1]), -def->range, def->range); - buff[2] = clamp_t(s16, le16_to_cpu(fval[2]), -def->range, def->range); + data->scan.channels[0] = clamp_t(s16, le16_to_cpu(fval[0]), -def->range, def->range); + data->scan.channels[1] = clamp_t(s16, le16_to_cpu(fval[1]), -def->range, def->range); + data->scan.channels[2] = clamp_t(s16, le16_to_cpu(fval[2]), -def->range, def->range);
- iio_push_to_buffers_with_timestamp(indio_dev, buff, + iio_push_to_buffers_with_timestamp(indio_dev, &data->scan, iio_get_time_ns(indio_dev)); + return;
unlock: