[PATCH] drm/i915: Fix possible int overflow in skl_ddi_calculate_wrpll()

[Nikita Zhandarovich]

On the off chance that clock value ends up being too high (by means
of skl_ddi_calculate_wrpll() having benn called with big enough
value of crtc_state->port_clock * 1000), one possible consequence
may be that the result will not be able to fit into signed int.

Fix this, albeit unlikely, issue by first casting one of the operands
to u32, then to u64, and thus avoid causing an integer overflow.

Found by Linux Verification Center (linuxtesting.org) with static
analysis tool SVACE.

Fixes: fe70b262e781 ("drm/i915: Move a bunch of stuff into rodata from the stack")
Cc: stable at vger.kernel.org
Signed-off-by: Nikita Zhandarovich <n.zhandarovich at fintech.ru>
---
Fixes: tag is not entirely correct, as I can't properly identify the
origin with all the code movement. I opted out for using the most
recent topical commit instead.

 drivers/gpu/drm/i915/display/intel_dpll_mgr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dpll_mgr.c b/drivers/gpu/drm/i915/display/intel_dpll_mgr.c
index 90998b037349..46d4dac6c491 100644
--- a/drivers/gpu/drm/i915/display/intel_dpll_mgr.c
+++ b/drivers/gpu/drm/i915/display/intel_dpll_mgr.c
@@ -1683,7 +1683,7 @@ skl_ddi_calculate_wrpll(int clock /* in Hz */,
 	};
 	unsigned int dco, d, i;
 	unsigned int p0, p1, p2;
-	u64 afe_clock = clock * 5; /* AFE Clock is 5x Pixel clock */
+	u64 afe_clock = (u64)(u32)clock * 5; /* AFE Clock is 5x Pixel clock */
 
 	for (d = 0; d < ARRAY_SIZE(dividers); d++) {
 		for (dco = 0; dco < ARRAY_SIZE(dco_central_freq); dco++) {