From 1a08662025587f5c9105d9d495ea71c9b7ab65b3 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Konrad=20Gr=C3=A4fe?= Date: Fri, 5 May 2023 16:36:40 +0200 Subject: [PATCH] usb: gadget: u_ether: Fix host MAC address case MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit commit 3c0f4f09c063e143822393d99cb2b19a85451c07 upstream. The CDC-ECM specification [1] requires to send the host MAC address as an uppercase hexadecimal string in chapter "5.4 Ethernet Networking Functional Descriptor": The Unicode character is chosen from the set of values 30h through 39h and 41h through 46h (0-9 and A-F). However, snprintf(.., "%pm", ..) generates a lowercase MAC address string. While most host drivers are tolerant to this, UsbNcm.sys on Windows 10 is not. Instead it uses a different MAC address with all bytes set to zero including and after the first byte containing a lowercase letter. On Windows 11 Microsoft fixed it, but apparently they did not backport the fix. This change fixes the issue by upper-casing the MAC to comply with the specification. [1]: https://www.usb.org/document-library/class-definitions-communication-devices-12, file ECM120.pdf Fixes: 95a5cf8b4900 ("usb: gadget: u_ether: construct with default values and add setters/getters") Cc: stable@vger.kernel.org Signed-off-by: Konrad Gräfe Link: https://lore.kernel.org/r/20230505143640.443014-1-k.graefe@gateware.de Signed-off-by: Greg Kroah-Hartman --- drivers/usb/gadget/function/u_ether.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/usb/gadget/function/u_ether.c b/drivers/usb/gadget/function/u_ether.c index e06022873df16..1f420ff8f4232 100644 --- a/drivers/usb/gadget/function/u_ether.c +++ b/drivers/usb/gadget/function/u_ether.c @@ -17,6 +17,7 @@ #include #include #include +#include #include "u_ether.h" @@ -978,6 +979,8 @@ int gether_get_host_addr_cdc(struct net_device *net, char *host_addr, int len) dev = netdev_priv(net); snprintf(host_addr, len, "%pm", dev->host_mac); + string_upper(host_addr, host_addr); + return strlen(host_addr); } EXPORT_SYMBOL_GPL(gether_get_host_addr_cdc); -- 2.39.5