[PATCH] staging: iio: frequency: ad9832: fix division by zero in ad9832_calc_freqreg()

From: Zicheng Qu
Date: Tue Oct 22 2024 - 09:43:54 EST


In the ad9832_write_frequency() function, clk_get_rate() might return 0.
This can lead to a division by zero when calling ad9832_calc_freqreg().
The check if (fout > (clk_get_rate(st->mclk) / 2)) does not protect
against the case when fout is 0. The ad9832_write_frequency() function
is called from ad9832_write(), and fout is derived from a text buffer,
which can contain any value.

Link: https://lore.kernel.org/all/2024100904-CVE-2024-47663-9bdc@gregkh/
Fixes: ea707584bac1 ("Staging: IIO: DDS: AD9832 / AD9835 driver")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Zicheng Qu <quzicheng@xxxxxxxxxx>
Reviewed-by: Nuno Sa <nuno.sa@xxxxxxxxxx>
Reviewed-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Link: https://patch.msgid.link/20241022134354.574614-1-quzicheng@xxxxxxxxxx
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
---
drivers/staging/iio/frequency/ad9832.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/iio/frequency/ad9832.c b/drivers/staging/iio/frequency/ad9832.c
index 6c390c4eb26de..492612e8f8bad 100644
--- a/drivers/staging/iio/frequency/ad9832.c
+++ b/drivers/staging/iio/frequency/ad9832.c
@@ -129,12 +129,15 @@ static unsigned long ad9832_calc_freqreg(unsigned long mclk, unsigned long fout)
static int ad9832_write_frequency(struct ad9832_state *st,
unsigned int addr, unsigned long fout)
{
+ unsigned long clk_freq;
unsigned long regval;

- if (fout > (clk_get_rate(st->mclk) / 2))
+ clk_freq = clk_get_rate(st->mclk);
+
+ if (!clk_freq || fout > (clk_freq / 2))
return -EINVAL;

- regval = ad9832_calc_freqreg(clk_get_rate(st->mclk), fout);
+ regval = ad9832_calc_freqreg(clk_freq, fout);

st->freq_data[0] = cpu_to_be16((AD9832_CMD_FRE8BITSW << CMD_SHIFT) |
(addr << ADD_SHIFT) |
--
2.43.0