| Message ID | 20211026084208.2574-1-jani.nikula@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/i915/dp: fix integer overflow in 128b/132b data rate calculation | expand |
On Tue, Oct 26, 2021 at 11:42:07AM +0300, Jani Nikula wrote: > The intermediate value 1000000 * 10 * 9671 overflows 32 bits, so force > promotion to a bigger type. > > >From the logs: > > [drm:intel_dp_compute_config [i915]] DP link rate required 3657063 available -580783288 > > Fixes: 48efd014f0ea ("drm/i915/dp: add max data rate calculation for UHBR rates") > Cc: Manasi Navare <manasi.d.navare@intel.com> > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com> > Signed-off-by: Jani Nikula <jani.nikula@intel.com> > --- > drivers/gpu/drm/i915/display/intel_dp.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c > index f5dc2126d140..9a0cd2e1ebea 100644 > --- a/drivers/gpu/drm/i915/display/intel_dp.c > +++ b/drivers/gpu/drm/i915/display/intel_dp.c > @@ -352,7 +352,7 @@ intel_dp_max_data_rate(int max_link_rate, int max_lanes) > */ > int max_link_rate_kbps = max_link_rate * 10; > > - max_link_rate_kbps = DIV_ROUND_CLOSEST_ULL(max_link_rate_kbps * 9671, 10000); > + max_link_rate_kbps = DIV_ROUND_CLOSEST_ULL(max_link_rate_kbps * 9671UL, 10000UL); UL is not 64bit on 32bit architectures. Also having a 64bit divisor would be wasteful. DIV_ROUND_CLOSEST_ULL(mul_u32_u32(...), 10000); > max_link_rate = max_link_rate_kbps / 8; > } > > -- > 2.30.2
diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c index f5dc2126d140..9a0cd2e1ebea 100644 --- a/drivers/gpu/drm/i915/display/intel_dp.c +++ b/drivers/gpu/drm/i915/display/intel_dp.c @@ -352,7 +352,7 @@ intel_dp_max_data_rate(int max_link_rate, int max_lanes) */ int max_link_rate_kbps = max_link_rate * 10; - max_link_rate_kbps = DIV_ROUND_CLOSEST_ULL(max_link_rate_kbps * 9671, 10000); + max_link_rate_kbps = DIV_ROUND_CLOSEST_ULL(max_link_rate_kbps * 9671UL, 10000UL); max_link_rate = max_link_rate_kbps / 8; }
The intermediate value 1000000 * 10 * 9671 overflows 32 bits, so force promotion to a bigger type. From the logs: [drm:intel_dp_compute_config [i915]] DP link rate required 3657063 available -580783288 Fixes: 48efd014f0ea ("drm/i915/dp: add max data rate calculation for UHBR rates") Cc: Manasi Navare <manasi.d.navare@intel.com> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com> Signed-off-by: Jani Nikula <jani.nikula@intel.com> --- drivers/gpu/drm/i915/display/intel_dp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)