[PATCH] iio: frequency: admv1013: fix NULL pointer dereference on str

[Antoniu Miclaus <antoniu.miclaus@analog.com>]

When device_property_read_string() fails, str is left uninitialized
but the code falls through to strcmp(str, ...), dereferencing a garbage
pointer. Replace manual read/strcmp with device_property_match_string()
which handles the missing property case internally.

Fixes: da35a7b526d9 ("iio: frequency: admv1013: add support for ADMV1013")
Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
---
 drivers/iio/frequency/admv1013.c | 23 +++++------------------
 1 file changed, 5 insertions(+), 18 deletions(-)

diff --git a/drivers/iio/frequency/admv1013.c b/drivers/iio/frequency/admv1013.c
index 9202443ef445..a1f88138939d 100644
--- a/drivers/iio/frequency/admv1013.c
+++ b/drivers/iio/frequency/admv1013.c
@@ -515,34 +515,21 @@ static void admv1013_powerdown(void *data)
 static int admv1013_properties_parse(struct admv1013_state *st)
 {
 	int ret;
-	const char *str;
 	struct device *dev = &st->spi->dev;
 
 	st->det_en = device_property_read_bool(dev, "adi,detector-enable");
 
-	ret = device_property_read_string(dev, "adi,input-mode", &str);
-	if (ret)
-		st->input_mode = ADMV1013_IQ_MODE;
-
-	if (!strcmp(str, "iq"))
-		st->input_mode = ADMV1013_IQ_MODE;
-	else if (!strcmp(str, "if"))
+	if (device_property_match_string(dev, "adi,input-mode", "if") >= 0)
 		st->input_mode = ADMV1013_IF_MODE;
 	else
-		return -EINVAL;
-
-	ret = device_property_read_string(dev, "adi,quad-se-mode", &str);
-	if (ret)
-		st->quad_se_mode = ADMV1013_SE_MODE_DIFF;
+		st->input_mode = ADMV1013_IQ_MODE;
 
-	if (!strcmp(str, "diff"))
-		st->quad_se_mode = ADMV1013_SE_MODE_DIFF;
-	else if (!strcmp(str, "se-pos"))
+	if (device_property_match_string(dev, "adi,quad-se-mode", "se-pos") >= 0)
 		st->quad_se_mode = ADMV1013_SE_MODE_POS;
-	else if (!strcmp(str, "se-neg"))
+	else if (device_property_match_string(dev, "adi,quad-se-mode", "se-neg") >= 0)
 		st->quad_se_mode = ADMV1013_SE_MODE_NEG;
 	else
-		return -EINVAL;
+		st->quad_se_mode = ADMV1013_SE_MODE_DIFF;
 
 	ret = devm_regulator_bulk_get_enable(dev,
 					     ARRAY_SIZE(admv1013_vcc_regs),
-- 
2.43.0