media: dib8000: avoid division by 0 in dib8000_set_dds()

commit dde3c37 upstream.

In dib8000_set_dds(), 1 << 26 (67108864) divided by e.g. 1 apparently can't
fit into 16-bit variable unit_khz_dds_val, being truncated to 0; this will
cause division by 0 while calling dprintk() with debugging enabled (via the
module parameter).  Use s32 instead of s16 to declare the variable, getting
rid of the cast to u16 in the *else* branch as well...

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

Fixes: 173a64c ("[media] dib8000: enhancement")
Cc: stable@vger.kernel.org
Signed-off-by: Sergey Shtylyov <s.shtylyov@auroraos.dev>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Sergey Shtylyov

drivers/media/dvb-frontends/dib8000.c

@@ -2694,7 +2694,7 @@ static void dib8000_viterbi_state(struct dib8000_state *state, u8 onoff)
 
 static void dib8000_set_dds(struct dib8000_state *state, s32 offset_khz)
 {
-	s16 unit_khz_dds_val;
+	s32 unit_khz_dds_val;
 	u32 abs_offset_khz = abs(offset_khz);
 	u32 dds = state->cfg.pll->ifreq & 0x1ffffff;
 	u8 invert = !!(state->cfg.pll->ifreq & (1 << 25));
@@ -2715,7 +2715,7 @@ static void dib8000_set_dds(struct dib8000_state *state, s32 offset_khz)
 			dds = (1<<26) - dds;
 	} else {
 		ratio = 2;
-		unit_khz_dds_val = (u16) (67108864 / state->cfg.pll->internal);
+		unit_khz_dds_val = 67108864 / state->cfg.pll->internal;
 
 		if (offset_khz < 0)
 			unit_khz_dds_val *= -1;