linux-kernel - [PATCH RFT] media: dib8000: avoid division by 0 in dib8000_set

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Message-ID: <20260206142237.13040-1-s.shtylyov@auroraos.dev>
Date: Fri, 6 Feb 2026 17:22:26 +0300
From: Sergey Shtylyov <s.shtylyov@...oraos.dev>
To: Mauro Carvalho Chehab <mchehab@...nel.org>, <linux-media@...r.kernel.org>
CC: Sergey Shtylyov <s.shtylyov@...oraos.dev>, Olivier Grenie
	<olivier.grenie@...rot.com>, Patrick Boettcher <pboettcher@...nellabs.com>,
	<linux-kernel@...r.kernel.org>
Subject: [PATCH RFT] media: dib8000: avoid division by 0 in dib8000_set_dds()

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: 173a64cb3fcf ("[media] dib8000: enhancement")
Signed-off-by: Sergey Shtylyov <s.shtylyov@...oraos.dev>

---
The patch is against the fixes branch of the linuxtv.org/media.git repo...

 drivers/media/dvb-frontends/dib8000.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/media/dvb-frontends/dib8000.c b/drivers/media/dvb-frontends/dib8000.c
index d90f1b0b2051..f4e963cdb7f2 100644
--- a/drivers/media/dvb-frontends/dib8000.c
+++ b/drivers/media/dvb-frontends/dib8000.c
@@ -2695,7 +2695,7 @@ 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));
@@ -2716,7 +2716,7 @@ 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;
-- 
2.52.0