[PATCH] HID: picolcd: prevent NULL pointer dereference in picolcd_send_and_wait()

[Georgiy Osokin <g.osokin@auroraos.dev>]

In picolcd_send_and_wait(), an integer overflow of the signed loop counter
'k' can theoretically lead to a NULL pointer dereference of 'raw_data'.
If the loop executes more than INT_MAX times, 'k' becomes negative,
making the condition 'k < size' true even when 'size' is 0.

Change the type of 'k' to 'unsigned int' to prevent the overflow and
eliminate the out-of-bounds access.

Found by Linux Verification Center (linuxtesting.org) with the Svace static
analysis tool.

Fixes: fabdbf2 ("HID: picoLCD: split driver code")
Signed-off-by: Georgiy Osokin <g.osokin@auroraos.dev>

---
 drivers/hid/hid-picolcd_core.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/hid/hid-picolcd_core.c b/drivers/hid/hid-picolcd_core.c
index 2cc01e1bc1a8..d73e97c8b853 100644
--- a/drivers/hid/hid-picolcd_core.c
+++ b/drivers/hid/hid-picolcd_core.c
@@ -72,7 +72,8 @@ struct picolcd_pending *picolcd_send_and_wait(struct hid_device *hdev,
 	struct picolcd_pending *work;
 	struct hid_report *report = picolcd_out_report(report_id, hdev);
 	unsigned long flags;
-	int i, j, k;
+	int i, j;
+	unsigned int k;
 
 	if (!report || !data)
 		return NULL;
-- 
2.50.1