usb: gadget: f_ncm: Fix MAC assignment NCM ethernet

[ Upstream commit 956606bafb5fc6e5968aadcda86fc0037e1d7548 ]

This fix is already present in f_ecm.c and was never
propagated to f_ncm.c

When creating multiple NCM ethernet devices
on a composite usb gadget device
each MAC address on the HOST side will be identical.
Having the same MAC on different network interfaces is bad.

This fix updates the MAC address inside the
ncm_strings_defs global during the ncm_bind call.
This ensures each device has a unique MAC.
In f_ecm.c ecm_string_defs is updated in the same way.

The defunct MAC assignment in ncm_alloc has been removed.

Signed-off-by: raub camaioni <raubcameo@gmail.com>
Link: https://lore.kernel.org/r/20250815131358.1047525-1-raubcameo@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/usb/gadget/function/f_ncm.c b/drivers/usb/gadget/function/f_ncm.c
index 3afc9a622086c2189ce2163a9a474205e52f121e..28e57d93973ace934c128607b70bf6fa8a2e9a10 100644 (file)
--- a/drivers/usb/gadget/function/f_ncm.c
+++ b/drivers/usb/gadget/function/f_ncm.c
@@ -1464,6 +1464,8 @@ static int ncm_bind(struct usb_configuration *c, struct usb_function *f)
 
        ncm_opts->bound = true;
 
+       ncm_string_defs[1].s = ncm->ethaddr;
+
        us = usb_gstrings_attach(cdev, ncm_strings,
                                 ARRAY_SIZE(ncm_string_defs));
        if (IS_ERR(us))
@@ -1759,7 +1761,6 @@ static struct usb_function *ncm_alloc(struct usb_function_instance *fi)
                mutex_unlock(&opts->lock);
                return ERR_PTR(-EINVAL);
        }
-       ncm_string_defs[STRING_MAC_IDX].s = ncm->ethaddr;
 
        spin_lock_init(&ncm->lock);
        ncm_reset_values(ncm);