[PATCH][next] iio: hw_consumer: Use struct_size() helper in kzalloc()

[PATCH][next] iio: hw_consumer: Use struct_size() helper in kzalloc()

[Gustavo A. R. Silva]

Make use of the struct_size() helper instead of an open-coded version,
in order to avoid any potential type mistakes or integer overflows that,
in the worst scenario, could lead to heap overflows.

Also, address the following sparse warnings:
drivers/iio/buffer/industrialio-hw-consumer.c:63:23: warning: using sizeof on a flexible structure

Link: https://github.com/KSPP/linux/issues/174
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
 drivers/iio/buffer/industrialio-hw-consumer.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/iio/buffer/industrialio-hw-consumer.c b/drivers/iio/buffer/industrialio-hw-consumer.c
index 87d9aabd20c7..fb58f599a80b 100644
--- a/drivers/iio/buffer/industrialio-hw-consumer.c
+++ b/drivers/iio/buffer/industrialio-hw-consumer.c
@@ -52,7 +52,6 @@ static const struct iio_buffer_access_funcs iio_hw_buf_access = {
 static struct hw_consumer_buffer *iio_hw_consumer_get_buffer(
 	struct iio_hw_consumer *hwc, struct iio_dev *indio_dev)
 {
-	size_t mask_size = BITS_TO_LONGS(indio_dev->masklength) * sizeof(long);
 	struct hw_consumer_buffer *buf;
 
 	list_for_each_entry(buf, &hwc->buffers, head) {
@@ -60,7 +59,8 @@ static struct hw_consumer_buffer *iio_hw_consumer_get_buffer(
 			return buf;
 	}
 
-	buf = kzalloc(sizeof(*buf) + mask_size, GFP_KERNEL);
+	buf = kzalloc(struct_size(buf, scan_mask, BITS_TO_LONGS(indio_dev->masklength)),
+		      GFP_KERNEL);
 	if (!buf)
 		return NULL;
 
-- 
2.27.0

Re: [PATCH][next] iio: hw_consumer: Use struct_size() helper in kzalloc()

[Kees Cook]

On Thu, Jan 20, 2022 at 04:52:43PM -0600, Gustavo A. R. Silva wrote:
> Make use of the struct_size() helper instead of an open-coded version,
> in order to avoid any potential type mistakes or integer overflows that,
> in the worst scenario, could lead to heap overflows.
> 
> Also, address the following sparse warnings:
> drivers/iio/buffer/industrialio-hw-consumer.c:63:23: warning: using sizeof on a flexible structure
> 
> Link: https://github.com/KSPP/linux/issues/174
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Looks good to me.

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook

Re: [PATCH][next] iio: hw_consumer: Use struct_size() helper in kzalloc()

[Jonathan Cameron]

On Thu, 20 Jan 2022 15:33:14 -0800
Kees Cook <keescook@chromium.org> wrote:

> On Thu, Jan 20, 2022 at 04:52:43PM -0600, Gustavo A. R. Silva wrote:
> > Make use of the struct_size() helper instead of an open-coded version,
> > in order to avoid any potential type mistakes or integer overflows that,
> > in the worst scenario, could lead to heap overflows.
> > 
> > Also, address the following sparse warnings:
> > drivers/iio/buffer/industrialio-hw-consumer.c:63:23: warning: using sizeof on a flexible structure
> > 
> > Link: https://github.com/KSPP/linux/issues/174
> > Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>  
> 
> Looks good to me.
> 
> Reviewed-by: Kees Cook <keescook@chromium.org>
> 
Good thing to tidy up, but I'm a little curious why I'm not
seeing these reports with latest sparse?
Ah. Found it via the report linked
CF='-Wflexible-array-sizeof'

Probably worth mentioned that in the patch descriptions. I've added it
to this one. 

I'm still setting the sparse report even with this patch.

What am I missing?

Jonathan