linux-kernel - [PATCH 16/22] media: dib8000: Prevent divide-by-zero in dib8000_set

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Message-ID: <bd1d504d930ae3f073b1e071bcf62cae7708773c.1742852847.git.jpoimboe@kernel.org>
Date: Mon, 24 Mar 2025 14:56:06 -0700
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: x86@...nel.org
Cc: linux-kernel@...r.kernel.org,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Miroslav Benes <mbenes@...e.cz>,
	Brendan Jackman <jackmanb@...gle.com>,
	Nathan Chancellor <nathan@...nel.org>,
	Mauro Carvalho Chehab <mchehab@...nel.org>,
	kernel test robot <lkp@...el.com>
Subject: [PATCH 16/22] media: dib8000: Prevent divide-by-zero in dib8000_set_dds()

If dib8000_set_dds()'s call to dib8000_read32() returns zero, the result
is a divide-by-zero.  Prevent that from happening.

Fixes the following warning with an UBSAN kernel:

  drivers/media/dvb-frontends/dib8000.o: warning: objtool: dib8000_tune() falls through to next function dib8096p_cfg_DibRx()

Cc: Mauro Carvalho Chehab <mchehab@...nel.org>
Fixes: 173a64cb3fcf ("[media] dib8000: enhancement")
Reported-by: kernel test robot <lkp@...el.com>
Closes: https://lore.kernel.org/r/202503210602.fvH5DO1i-lkp@intel.com/
Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
---
 drivers/media/dvb-frontends/dib8000.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/media/dvb-frontends/dib8000.c b/drivers/media/dvb-frontends/dib8000.c
index 2f5165918163..cfe59c3255f7 100644
--- a/drivers/media/dvb-frontends/dib8000.c
+++ b/drivers/media/dvb-frontends/dib8000.c
@@ -2701,8 +2701,11 @@ static void dib8000_set_dds(struct dib8000_state *state, s32 offset_khz)
 	u8 ratio;
 
 	if (state->revision == 0x8090) {
+		u32 internal = dib8000_read32(state, 23) / 1000;
+
 		ratio = 4;
-		unit_khz_dds_val = (1<<26) / (dib8000_read32(state, 23) / 1000);
+
+		unit_khz_dds_val = (1<<26) / (internal ?: 1);
 		if (offset_khz < 0)
 			dds = (1 << 26) - (abs_offset_khz * unit_khz_dds_val);
 		else
-- 
2.48.1