Patch "usb: gadget: u_ether: Fix host MAC address case" has been added to the 5.4-stable tree

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This is a note to let you know that I've just added the patch titled

    usb: gadget: u_ether: Fix host MAC address case

to the 5.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     usb-gadget-u_ether-fix-host-mac-address-case.patch
and it can be found in the queue-5.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit d3a0a436d0cea7e59ed2a33a98e0d417764a9567
Author: Konrad Gräfe <k.graefe@xxxxxxxxxxx>
Date:   Fri May 5 16:36:40 2023 +0200

    usb: gadget: u_ether: Fix host MAC address case
    
    [ Upstream commit 3c0f4f09c063e143822393d99cb2b19a85451c07 ]
    
    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: bcd4a1c40bee ("usb: gadget: u_ether: construct with default values and add setters/getters")
    Cc: stable@xxxxxxxxxxxxxxx
    Signed-off-by: Konrad Gräfe <k.graefe@xxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20230505143640.443014-1-k.graefe@xxxxxxxxxxx
    Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/usb/gadget/function/u_ether.c b/drivers/usb/gadget/function/u_ether.c
index d9f9c7a678d8b..af3cb3bfdc29a 100644
--- a/drivers/usb/gadget/function/u_ether.c
+++ b/drivers/usb/gadget/function/u_ether.c
@@ -17,6 +17,7 @@
 #include <linux/etherdevice.h>
 #include <linux/ethtool.h>
 #include <linux/if_vlan.h>
+#include <linux/string_helpers.h>
 #include <linux/usb/composite.h>
 
 #include "u_ether.h"
@@ -940,6 +941,8 @@ 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);



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