Re: [PATCH] drm/bridge: nwl-dsi: Avoid potential multiplication overflow on 32-bit

Hi Geert,

On Mon, Jan 11, 2021 at 10:02 AM Geert Uytterhoeven geert+renesas@glider.be wrote:

As nwl_dsi.lanes is u32, and NSEC_PER_SEC is 1000000000L, the second multiplication in

dsi->lanes * 8 * NSEC_PER_SEC

will overflow on a 32-bit platform. Fix this by making the constant unsigned long long, forcing 64-bit arithmetic.

While iMX8 is arm64, this driver is currently used on 64-bit platforms only, where long is 64-bit, so this cannot happen. But the issue may start to happen when the driver is reused for a 32-bit SoC, or when code is copied for a new driver.

This IP is also present on i.MX7ULP, which is 32-bit, but not supported yet.

Thanks for taking care of this.

Reviewed-by: Fabio Estevam festevam@gmail.com