[tip: objtool/urgent] objtool, media: dib8000: Prevent divide-by-zero in dib8000_set_dds()

[tip-bot2 for Josh Poimboeuf]

The following commit has been merged into the objtool/urgent branch of tip:

Commit-ID:     e63d465f59011dede0a0f1d21718b59a64c3ff5c
Gitweb:        https://git.kernel.org/tip/e63d465f59011dede0a0f1d21718b59a64c3ff5c
Author:        Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
AuthorDate:    Mon, 24 Mar 2025 14:56:06 -07:00
Committer:     Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Tue, 25 Mar 2025 23:00:15 +01:00

objtool, 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()

Fixes: 173a64cb3fcf ("[media] dib8000: enhancement")
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/bd1d504d930ae3f073b1e071bcf62cae7708773c.1742852847.git.jpoimboe@xxxxxxxxxx
Closes: https://lore.kernel.org/r/202503210602.fvH5DO1i-lkp@xxxxxxxxx/
---
 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 2f51659..cfe59c3 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