From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from outboundhk.mxmail.xiaomi.com (unknown [207.226.244.123]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 4B4F6221DB5; Thu, 26 Mar 2026 13:13:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=207.226.244.123 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774530842; cv=none; b=HRHwWRq1ong5w9sOZhXLgn9yFT1GwfWo3YnjOTOpkQo47+ZFLVT3YYFtbMJr8aHGET16nUuY299XTNbJoG9+sjghz3f2lOCx165H+PAjn6pQ0x2LsAS72keVTUqaji/dQIGgAMFHONjXinjsR6gj5FVaqh7kB7DoOT+9txtSrg8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774530842; c=relaxed/simple; bh=peJJaHsjLqEK05OjKSP0jF59iOfq+EQDL41e+emQEio=; h=Date:From:To:CC:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=kT/kt4bdkr4N3SvuSrf2pySK3obw44uphp6xPkf1aoShzPn5v7fI5dfBR10DIJgv8/uLd613G7Jjib3maRU9Zsj9W8nE1PmbHt6WMJ4/oAILJM0SyxVYeptyAtyt/+t2DAPepuThV85L2+OlqJ7KaVc+QPW78mbcjLCwHoL/3i0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=xiaomi.com; spf=pass smtp.mailfrom=xiaomi.com; arc=none smtp.client-ip=207.226.244.123 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=xiaomi.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=xiaomi.com X-CSE-ConnectionGUID: SoBTSYuVTQ6J1qgAiwfOXg== X-CSE-MsgGUID: Xy4JArEoRtC/t343N6rIdg== X-IronPort-AV: E=Sophos;i="6.23,142,1770566400"; d="scan'208";a="170857910" Date: Thu, 26 Mar 2026 21:13:46 +0800 From: Dayu Jiang To: Kuen-Han Tsai , Greg Kroah-Hartman CC: David Brownell , , , Subject: Re: [PATCH] usb: gadget: u_ether: Fix race between gether_disconnect and eth_stop Message-ID: References: <20260311-gether-disconnect-npe-v1-1-454966adf7c7@google.com> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="gbk" Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20260311-gether-disconnect-npe-v1-1-454966adf7c7@google.com> X-ClientProxiedBy: BJ-MBX06.mioffice.cn (10.237.8.126) To BJ-MBX03.mioffice.cn (10.237.8.123) On Wed, Mar 11, 2026 at 05:12:15PM +0800, Kuen-Han Tsai wrote: > 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. > Hi Greg, Hit the same issue during NCM switch stress test. Can you take a look at this patch and check if it¡¯s ready for merge? Thanks, Dayu Jiang > Fixes: 2b3d942c4878 ("usb ethernet gadget: split out network core") > Cc: stable@vger.kernel.org > Signed-off-by: Kuen-Han Tsai > --- > drivers/usb/gadget/function/u_ether.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/drivers/usb/gadget/function/u_ether.c b/drivers/usb/gadget/function/u_ether.c > index 338f6e2a85a9..2c970a0eafd9 100644 > --- a/drivers/usb/gadget/function/u_ether.c > +++ b/drivers/usb/gadget/function/u_ether.c > @@ -1246,6 +1246,11 @@ 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); > > @@ -1283,11 +1288,6 @@ 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); > > > --- > base-commit: 1be3b77de4eb89af8ae2fd6610546be778e25589 > change-id: 20260311-gether-disconnect-npe-5861d9831dff > > Best regards, > -- > Kuen-Han Tsai >