From: Kuen-Han Tsai Date: Wed, 11 Mar 2026 09:12:15 +0000 (+0800) Subject: usb: gadget: u_ether: Fix race between gether_disconnect and eth_stop X-Git-Tag: v7.0-rc7~10^2~35 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e1eabb072c75681f78312c484ccfffb7430f206e;p=thirdparty%2Fkernel%2Flinux.git usb: gadget: u_ether: Fix race between gether_disconnect and eth_stop A race condition between gether_disconnect() and eth_stop() leads to a NULL pointer dereference. Specifically, if eth_stop() is triggered concurrently while gether_disconnect() is tearing down the endpoints, eth_stop() attempts to access the cleared endpoint descriptor, causing the following NPE: Unable to handle kernel NULL pointer dereference Call trace: __dwc3_gadget_ep_enable+0x60/0x788 dwc3_gadget_ep_enable+0x70/0xe4 usb_ep_enable+0x60/0x15c eth_stop+0xb8/0x108 Because eth_stop() crashes while holding the dev->lock, the thread running gether_disconnect() fails to acquire the same lock and spins forever, resulting in a hardlockup: Core - Debugging Information for Hardlockup core(7) Call trace: queued_spin_lock_slowpath+0x94/0x488 _raw_spin_lock+0x64/0x6c gether_disconnect+0x19c/0x1e8 ncm_set_alt+0x68/0x1a0 composite_setup+0x6a0/0xc50 The root cause is that the clearing of dev->port_usb in gether_disconnect() is delayed until the end of the function. Move the clearing of dev->port_usb to the very beginning of gether_disconnect() while holding dev->lock. This cuts off the link immediately, ensuring eth_stop() will see dev->port_usb as NULL and safely bail out. Fixes: 2b3d942c4878 ("usb ethernet gadget: split out network core") Cc: stable Signed-off-by: Kuen-Han Tsai Link: https://patch.msgid.link/20260311-gether-disconnect-npe-v1-1-454966adf7c7@google.com Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/usb/gadget/function/u_ether.c b/drivers/usb/gadget/function/u_ether.c index 1a9e7c495e2e..23c7c0cdf202 100644 --- a/drivers/usb/gadget/function/u_ether.c +++ b/drivers/usb/gadget/function/u_ether.c @@ -1223,6 +1223,11 @@ void gether_disconnect(struct gether *link) DBG(dev, "%s\n", __func__); + spin_lock(&dev->lock); + dev->port_usb = NULL; + link->is_suspend = false; + spin_unlock(&dev->lock); + netif_stop_queue(dev->net); netif_carrier_off(dev->net); @@ -1260,11 +1265,6 @@ void gether_disconnect(struct gether *link) dev->header_len = 0; dev->unwrap = NULL; dev->wrap = NULL; - - spin_lock(&dev->lock); - dev->port_usb = NULL; - link->is_suspend = false; - spin_unlock(&dev->lock); } EXPORT_SYMBOL_GPL(gether_disconnect);