[PATCH] iio: adf4350: fix a possible divided-by-zero bug in adf4350_set_freq()

From: tq17373059
Date: Fri May 21 2021 - 02:26:25 EST


From: Qi Teng <tq17373059@xxxxxxxxxxx>

The variable st->r1_mod is checked in:
if (st->r0_fract && st->r1_mod)

This indicates that st->r1_mod can be zero. Its value is the same as
that in:
st->r0_fract = do_div(tmp, st->r1_mod);

However, st->r1_mod performs as a divisor in this statement, which
implies a possible divided-by-zero bug.

To fix this possible bug, st->r1_mod is checked before the division
operation. If it is zero, st->r0_fract is set to zero instead of
do_div(tmp, st->r1_mod).

Reported-by: TOTE Robot <oslab@xxxxxxxxxxxxxxx>
Signed-off-by: Qi Teng <tq17373059@xxxxxxxxxxx>
---
drivers/iio/frequency/adf4350.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/drivers/iio/frequency/adf4350.c b/drivers/iio/frequency/adf4350.c
index 99c6f260cc21..1462a6a5bc6d 100644
--- a/drivers/iio/frequency/adf4350.c
+++ b/drivers/iio/frequency/adf4350.c
@@ -182,10 +182,7 @@ static int adf4350_set_freq(struct adf4350_state *st, unsigned long long freq)

tmp = freq * (u64)st->r1_mod + (st->fpfd >> 1);
do_div(tmp, st->fpfd); /* Div round closest (n + d/2)/d */
- if (st->r1_mod)
- st->r0_fract = do_div(tmp, st->r1_mod);
- else
- st->r0_fract = 0;
+ st->r0_fract = do_div(tmp, st->r1_mod);
st->r0_int = tmp;
} while (mdiv > st->r0_int);

--
2.25.1