| Message ID | 20200915162049.36434-1-colin.king@canonical.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/rockchip: cdn-dp: fix sign extension on an int multiply for a u64 result | expand |
On Tue, Sep 15, 2020 at 9:20 AM Colin King <colin.king@canonical.com> wrote: > > From: Colin Ian King <colin.king@canonical.com> > > The variable bit_per_pix is a u8 and is promoted in the multiplication > to an int type and then sign extended to a u64. If the result of the > int multiplication is greater than 0x7fffffff then the upper 32 bits will > be set to 1 as a result of the sign extension. Avoid this by casting > tu_size_reg to u64 to avoid sign extension and also a potential overflow. > > Addresses-Coverity: ("Unintended sign extension") > Fixes: 1a0f7ed3abe2 ("drm/rockchip: cdn-dp: add cdn DP support for rk3399") > Signed-off-by: Colin Ian King <colin.king@canonical.com> Reviewed-by: Guenter Roeck <groeck@chromium.org> > --- > drivers/gpu/drm/rockchip/cdn-dp-reg.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/rockchip/cdn-dp-reg.c b/drivers/gpu/drm/rockchip/cdn-dp-reg.c > index 9d2163ef4d6e..33fb4d05c506 100644 > --- a/drivers/gpu/drm/rockchip/cdn-dp-reg.c > +++ b/drivers/gpu/drm/rockchip/cdn-dp-reg.c > @@ -658,7 +658,7 @@ int cdn_dp_config_video(struct cdn_dp_device *dp) > */ > do { > tu_size_reg += 2; > - symbol = tu_size_reg * mode->clock * bit_per_pix; > + symbol = (u64)tu_size_reg * mode->clock * bit_per_pix; > do_div(symbol, dp->max_lanes * link_rate * 8); > rem = do_div(symbol, 1000); > if (tu_size_reg > 64) { > -- > 2.27.0 >
On Tue, 15 Sep 2020 17:20:49 +0100, Colin King wrote: > The variable bit_per_pix is a u8 and is promoted in the multiplication > to an int type and then sign extended to a u64. If the result of the > int multiplication is greater than 0x7fffffff then the upper 32 bits will > be set to 1 as a result of the sign extension. Avoid this by casting > tu_size_reg to u64 to avoid sign extension and also a potential overflow. Applied, thanks! [1/1] drm/rockchip: cdn-dp: fix sign extension on an int multiply for a u64 result commit: ce0cb93a5adb283f577cd4661f511047b5e39028 Best regards,
diff --git a/drivers/gpu/drm/rockchip/cdn-dp-reg.c b/drivers/gpu/drm/rockchip/cdn-dp-reg.c index 9d2163ef4d6e..33fb4d05c506 100644 --- a/drivers/gpu/drm/rockchip/cdn-dp-reg.c +++ b/drivers/gpu/drm/rockchip/cdn-dp-reg.c @@ -658,7 +658,7 @@ int cdn_dp_config_video(struct cdn_dp_device *dp) */ do { tu_size_reg += 2; - symbol = tu_size_reg * mode->clock * bit_per_pix; + symbol = (u64)tu_size_reg * mode->clock * bit_per_pix; do_div(symbol, dp->max_lanes * link_rate * 8); rem = do_div(symbol, 1000); if (tu_size_reg > 64) {