[PATCH v4] media: i2c: ov02a10: fix endpoint parsing use-after-free

[Biren Pandya]

The ov02a10_check_hwcfg() function calls fwnode_handle_put(ep)
immediately after allocating and parsing the endpoint. However, it
subsequently calls fwnode_property_read_u32() using the same 'ep'
handle, leading to a potential use-after-free.

Additionally, reading the optional 'ovti,mipi-clock-voltage' property
used to overwrite the 'ret' variable. If the property was missing,
'ret' would become negative, and this failure code would be incorrectly
returned at the end of the function, causing probe to fail entirely.

Fix the use-after-free by moving fwnode_property_read_u32() before
the endpoint is parsed and freed. Avoid the error leak by not
assigning the result of fwnode_property_read_u32() to 'ret'.

Fixes: 91807efbe8ec ("media: i2c: add OV02A10 image sensor driver")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Biren Pandya <birenpandya@xxxxxxxxx>
Reviewed-by: Vladimir Zapolskiy <vladimir.zapolskiy@xxxxxxxxxx>
---
Changes in v4:
- Collapsed fwnode_property_read_u32() into a single line per Vladimir's review.

Changes in v3:
- Moved property reads before parse to avoid UAF.
- Fixed error leak by dropping assignment to ret.
- Added Fixes/Cc stable.
- Picked up Reviewed-by.
---
 drivers/media/i2c/ov02a10.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/drivers/media/i2c/ov02a10.c b/drivers/media/i2c/ov02a10.c
index 143dcfe104456..98f8fc5b6a5ae 100644
--- a/drivers/media/i2c/ov02a10.c
+++ b/drivers/media/i2c/ov02a10.c
@@ -820,18 +820,15 @@ static int ov02a10_check_hwcfg(struct device *dev, struct ov02a10 *ov02a10)
 	if (!ep)
 		return -ENXIO;
 
+	/* Optional indication of MIPI clock voltage unit */
+	if (!fwnode_property_read_u32(ep, "ovti,mipi-clock-voltage", &clk_volt))
+		ov02a10->mipi_clock_voltage = clk_volt;
+
 	ret = v4l2_fwnode_endpoint_alloc_parse(ep, &bus_cfg);
 	fwnode_handle_put(ep);
 	if (ret)
 		return ret;
 
-	/* Optional indication of MIPI clock voltage unit */
-	ret = fwnode_property_read_u32(ep, "ovti,mipi-clock-voltage",
-				       &clk_volt);
-
-	if (!ret)
-		ov02a10->mipi_clock_voltage = clk_volt;
-
 	for (i = 0; i < ARRAY_SIZE(link_freq_menu_items); i++) {
 		for (j = 0; j < bus_cfg.nr_of_link_frequencies; j++) {
 			if (link_freq_menu_items[i] ==
-- 
2.50.1 (Apple Git-155)