[PATCH v2] Bluetooth: bpa10x: avoid OOB read of revision string in bpa10x_setup()

[Weiming Shi <bestswngs@gmail.com>]

bpa10x_setup() sends the vendor command 0xfc0e and passes the response
to bt_dev_info() and hci_set_fw_info() as a "%s" string starting at
skb->data + 1, without checking the length:

	bt_dev_info(hdev, "%s", (char *)(skb->data + 1));
	hci_set_fw_info(hdev, "%s", skb->data + 1);

A device that returns a one-byte response (status only) leaves
skb->data + 1 past the end of the data, and the %s walk reads adjacent
slab memory until it meets a NUL. The same happens when the payload is
not NUL-terminated within skb->len. The out-of-bounds bytes end up in
the kernel log and the firmware-info debugfs file.

Print the revision string with a bounded "%.*s" limited to skb->len - 1
instead. This keeps the string readable for well-behaved devices while
never reading past the received data, and does not fail setup, so a
device returning a short or unterminated response keeps working.

Fixes: ddd68ec8f484 ("Bluetooth: bpa10x: Read revision information in setup stage")
Reported-by: Xiang Mei <xmei5@asu.edu>
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Weiming Shi <bestswngs@gmail.com>
---
v2: use bounded "%.*s" instead of failing setup with -EILSEQ (Pauli)
 drivers/bluetooth/bpa10x.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/bluetooth/bpa10x.c b/drivers/bluetooth/bpa10x.c
index 2ae38a321c4b..e63d1af250ec 100644
--- a/drivers/bluetooth/bpa10x.c
+++ b/drivers/bluetooth/bpa10x.c
@@ -255,9 +255,13 @@ static int bpa10x_setup(struct hci_dev *hdev)
 	if (IS_ERR(skb))
 		return PTR_ERR(skb);
 
-	bt_dev_info(hdev, "%s", (char *)(skb->data + 1));
+	/* Bounded print: the device controls skb->len. */
+	if (skb->len > 1) {
+		int len = skb->len - 1;
 
-	hci_set_fw_info(hdev, "%s", skb->data + 1);
+		bt_dev_info(hdev, "%.*s", len, (char *)(skb->data + 1));
+		hci_set_fw_info(hdev, "%.*s", len, skb->data + 1);
+	}
 
 	kfree_skb(skb);
 	return 0;
-- 
2.43.0