Re: [PATCH] Bluetooth: mark bacmp() and bacpy() as __always_inline

[Kees Cook <keescook@chromium.org>]

On Mon, Oct 09, 2023 at 08:23:08PM +0200, Arnd Bergmann wrote:
> On Mon, Oct 9, 2023, at 18:02, Kees Cook wrote:
> > On Mon, Oct 09, 2023 at 05:36:55PM +0200, Arnd Bergmann wrote:
> >> On Mon, Oct 9, 2023, at 15:48, Arnd Bergmann wrote:
> >> 
> >> Sorry, I have to retract this, something went wrong on my
> >> testing and I now see the same problem in some configs regardless
> >> of whether the patch is applied or not.
> >
> > Perhaps turn them into macros instead?
> 
> I just tried that and still see the problem even with the macro,
> so whatever gcc is doing must be a different issue. Maybe it
> has correctly found a codepath that triggers this?
> 
> If you are able to help debug the issue better,
> see these defconfigs for examples:
> 
> https://pastebin.com/raw/pC8Lnrn2
> https://pastebin.com/raw/yb965unC

This seems like a GCC bug. It is complaining about &hdev->bdaddr for
some reason. This silences it:

diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index 6f4409b4c364..509e86b36576 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -3266,6 +3266,7 @@ static void hci_conn_request_evt(struct hci_dev *hdev, void *data,
 	int mask = hdev->link_mode;
 	struct inquiry_entry *ie;
 	struct hci_conn *conn;
+	bdaddr_t a;
 	__u8 flags = 0;
 
 	bt_dev_dbg(hdev, "bdaddr %pMR type 0x%x", &ev->bdaddr, ev->link_type);
@@ -3273,7 +3274,8 @@ static void hci_conn_request_evt(struct hci_dev *hdev, void *data,
 	/* Reject incoming connection from device with same BD ADDR against
 	 * CVE-2020-26555
 	 */
-	if (!bacmp(&hdev->bdaddr, &ev->bdaddr)) {
+	a = hdev->bdaddr;
+	if (!bacmp(&a, &ev->bdaddr)) {
 		bt_dev_dbg(hdev, "Reject connection with same BD_ADDR %pMR\n",
 			   &ev->bdaddr);
 		hci_reject_conn(hdev, &ev->bdaddr);

:(

-- 
Kees Cook