[PATCH 6.12 202/242] usb: gadget: u_ether: Fix NULL pointer deref in eth_get_drvinfo

Greg Kroah-Hartman
2026-04-08T18:48:04Z

From: Kuen-Han Tsai <khtsai@google.com>

commit e002e92e88e12457373ed096b18716d97e7bbb20 upstream.

Commit ec35c1969650 ("usb: gadget: f_ncm: Fix net_device lifecycle with
device_move") reparents the gadget device to /sys/devices/virtual during
unbind, clearing the gadget pointer. If the userspace tool queries on
the surviving interface during this detached window, this leads to a
NULL pointer dereference.

Unable to handle kernel NULL pointer dereference
Call trace:
eth_get_drvinfo+0x50/0x90
ethtool_get_drvinfo+0x5c/0x1f0
__dev_ethtool+0xaec/0x1fe0
dev_ethtool+0x134/0x2e0
dev_ioctl+0x338/0x560

Add a NULL check for dev->gadget in eth_get_drvinfo(). When detached,
skip copying the fw_version and bus_info strings, which is natively
handled by ethtool_get_drvinfo for empty strings.

Suggested-by: Val Packett <val@packett.cool>
Reported-by: Val Packett <val@packett.cool>
Closes: https://lore.kernel.org/linux-usb/10890524-cf83-4a71-b879-93e2b2cc1fcc@packett.cool/
Fixes: ec35c1969650 ("usb: gadget: f_ncm: Fix net_device lifecycle with device_move")
Cc: stable <stable@kernel.org>
Signed-off-by: Kuen-Han Tsai <khtsai@google.com>
Link: https://patch.msgid.link/20260316-eth-null-deref-v1-1-07005f33be85@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/usb/gadget/function/u_ether.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

--- a/drivers/usb/gadget/function/u_ether.c
+++ b/drivers/usb/gadget/function/u_ether.c
@@ -112,8 +112,10 @@ static void eth_get_drvinfo(struct net_d

strscpy(p->driver, "g_ether", sizeof(p->driver));
strscpy(p->version, UETH__VERSION, sizeof(p->version));
- strscpy(p->fw_version, dev->gadget->name, sizeof(p->fw_version));
- strscpy(p->bus_info, dev_name(&dev->gadget->dev), sizeof(p->bus_info));
+ if (dev->gadget) {
+ strscpy(p->fw_version, dev->gadget->name, sizeof(p->fw_version));
+ strscpy(p->bus_info, dev_name(&dev->gadget->dev), sizeof(p->bus_info));
+ }
}

/* REVISIT can also support: