From nobody Fri Dec 19 13:50:36 2025 Received: from mail-pg1-f201.google.com (mail-pg1-f201.google.com [209.85.215.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 741232DA760 for ; Tue, 14 Oct 2025 08:52:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760431923; cv=none; b=rbl6RGzuQEDy9sStXeQHXjcWkrIEA0J6B5S4zYEpB+fyWZla5b3dZ5W80LBleOClCrCb0iv9dhCXAclh2YR8zzbQZ1G7KM74pIUQy6RccXzQrsRn0MEzr8bHgfNv3u3VNnaQrc+n1cxmtdbCOYzQm4lKGuym3JPqAQR2sbuI2qA= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760431923; c=relaxed/simple; bh=PxY9YI4CSmdKhC6uoizpHkfwmH3aq/ev/ew2lUtOZuE=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=h7EhDKxI4dLopmm3oL9HOB6tWSu/ra9RUEJIwgDiW+tCUSHeRT3LDNc8JBQ3T1weI4tqrP5ut7fQ+OkwPjAhvUeftWaTnL+444H5iD7u/TckSz38TMDdRmEXlxHnn4frxywlzt4iOYVsw1kWoomRGVmFEBcTQarnsLLRJGbmgOk= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--hhhuuu.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=HWEAtvBK; arc=none smtp.client-ip=209.85.215.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--hhhuuu.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="HWEAtvBK" Received: by mail-pg1-f201.google.com with SMTP id 41be03b00d2f7-b5533921eb2so7128499a12.0 for ; Tue, 14 Oct 2025 01:52:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1760431921; x=1761036721; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=bX12dqdVlICTMSRoW5hHUvlBwoKcGr52PuS1MGrj6wY=; b=HWEAtvBKRJzCwsZpxc8cEQk4D5VsMXPcLM6KNQ74Er9O9GSI9uCAPLdY0IFN32YzFr 4ghCsTFcxdncomvoRBPcGxPgrpAxhcYmthssDlwVRkRhuGGl0pOB/PjpV5+059WmgM0l XnygJbTwelO3cFA2qZm31JaY1xtQZ4AE+raeDVDePw+3tmatL5XZ3Wnd7BbfeuIxkziY hD8PfvnZhspoD5uN9OOGj800lNtSVkOuu0LBnlWJJQKuhpRt4AUVO8d7R8V1cCHClspH dg2Jj6clC5R2wOtWwAUFTw7Z/MycARw6arxWyl+1palnv4xpGUMmuwvFBYjn90fuz+KR EmQg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1760431921; x=1761036721; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=bX12dqdVlICTMSRoW5hHUvlBwoKcGr52PuS1MGrj6wY=; b=jxD2p9Ia32SWOJIvRxEXWcDy9atuq0yByfj2bsK+SYMPBZEL9fOaEu/mM9CfTzNDff 9p58bU+LiOPbirhC7BW5PUDXvKdPH7npqQqpAd5i1SXpJVwOmrSHG4mYozevEiz0XX7J ksIl4NQnT88ZhOIt15NSGG7VUP8GEeac3kuYFhSZ/WlcPswqCSU8rV8/uBF+u8/YmX8J w0P2ooSYCKVfDLxarlU75vGEYgP21EHlHwG8uIkQR1ASIENkvsJ9ATWH17XUpGdqPDsW 9EPMU1H3WRdjeW18BEHO8UNLWaosWPO5KpPtiAv4fIvqlOCbysCrXoHOOwN1JJ7F0vA8 Q7AA== X-Forwarded-Encrypted: i=1; AJvYcCWp6PDhKsisgNxOCqV5Imyusatc8BzI7J6yThBGvTLWoVO4FThuSHb5Eid7qX0tw71qiNFHcR6TXA7YK1g=@vger.kernel.org X-Gm-Message-State: AOJu0YxOCWUO6xfo2EK6y81Xy4WXA9OIw4Pmx6L/zUrKNVTt6PASKhMr mXM8PqbaifH7asrZtMuO7pmGDqWZ41eK7m6in1bOPpiNfD3atPIsX/JK5JWRoGeXFVMOjtaYE0C 1EAdwiA== X-Google-Smtp-Source: AGHT+IG+Fi46f+lO8zssLsTmLd69T+nbCbw1cECTScqiKJBBv7O5leY+nhhN6mss+yBFIX4Zx7GK1+Ok9KU= X-Received: from plbka8.prod.google.com ([2002:a17:903:3348:b0:290:28e2:ce54]) (user=hhhuuu job=prod-delivery.src-stubby-dispatcher) by 2002:a17:903:2f0e:b0:248:a642:eec6 with SMTP id d9443c01a7336-29027402f2dmr259664015ad.50.1760431920649; Tue, 14 Oct 2025 01:52:00 -0700 (PDT) Date: Tue, 14 Oct 2025 08:51:56 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.51.0.760.g7b8bcc2412-goog Message-ID: <20251014085156.2651449-1-hhhuuu@google.com> Subject: [PATCH v2] usb: gadget: udc: fix race condition in usb_del_gadget From: Jimmy Hu To: gregkh@linuxfoundation.org, linux-usb@vger.kernel.org Cc: badhri@google.com, hhhuuu@google.com, stern@rowland.harvard.edu, royluo@google.com, Thinh.Nguyen@synopsys.com, balbi@ti.com, linux-kernel@vger.kernel.org, stable@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" A race condition during gadget teardown can lead to a use-after-free in usb_gadget_state_work(), as reported by KASAN: BUG: KASAN: invalid-access in sysfs_notify+0_x_2c/0_x_d0 Workqueue: events usb_gadget_state_work The fundamental race occurs because a concurrent event (e.g., an interrupt) can call usb_gadget_set_state() and schedule gadget->work at any time during the cleanup process in usb_del_gadget(). Commit 399a45e5237c ("usb: gadget: core: flush gadget workqueue after device removal") attempted to fix this by moving flush_work() to after device_del(). However, this does not fully solve the race, as a new work item can still be scheduled *after* flush_work() completes but before the gadget's memory is freed, leading to the same use-after-free. This patch fixes the race condition robustly by introducing a 'teardown' flag and a 'state_lock' spinlock to the usb_gadget struct. The flag is set during cleanup in usb_del_gadget() *before* calling flush_work() to prevent any new work from being scheduled once cleanup has commenced. The scheduling site, usb_gadget_set_state(), now checks this flag under the lock before queueing the work, thus safely closing the race window. Changes in v2: - Removed redundant inline comments as suggested by Alan Stern. Fixes: 5702f75375aa9 ("usb: gadget: udc-core: move sysfs_notify() to a work= queue") Signed-off-by: Jimmy Hu Cc: stable@vger.kernel.org Reviewed-by: Alan Stern --- drivers/usb/gadget/udc/core.c | 17 ++++++++++++++++- include/linux/usb/gadget.h | 5 +++++ 2 files changed, 21 insertions(+), 1 deletion(-) diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c index d709e24c1fd4..66d2428835da 100644 --- a/drivers/usb/gadget/udc/core.c +++ b/drivers/usb/gadget/udc/core.c @@ -1123,8 +1123,13 @@ static void usb_gadget_state_work(struct work_struct= *work) void usb_gadget_set_state(struct usb_gadget *gadget, enum usb_device_state state) { + unsigned long flags; + + spin_lock_irqsave(&gadget->state_lock, flags); gadget->state =3D state; - schedule_work(&gadget->work); + if (!gadget->teardown) + schedule_work(&gadget->work); + spin_unlock_irqrestore(&gadget->state_lock, flags); } EXPORT_SYMBOL_GPL(usb_gadget_set_state); =20 @@ -1357,6 +1362,8 @@ static void usb_udc_nop_release(struct device *dev) void usb_initialize_gadget(struct device *parent, struct usb_gadget *gadge= t, void (*release)(struct device *dev)) { + spin_lock_init(&gadget->state_lock); + gadget->teardown =3D false; INIT_WORK(&gadget->work, usb_gadget_state_work); gadget->dev.parent =3D parent; =20 @@ -1531,6 +1538,7 @@ EXPORT_SYMBOL_GPL(usb_add_gadget_udc); void usb_del_gadget(struct usb_gadget *gadget) { struct usb_udc *udc =3D gadget->udc; + unsigned long flags; =20 if (!udc) return; @@ -1544,6 +1552,13 @@ void usb_del_gadget(struct usb_gadget *gadget) kobject_uevent(&udc->dev.kobj, KOBJ_REMOVE); sysfs_remove_link(&udc->dev.kobj, "gadget"); device_del(&gadget->dev); + /* + * Set the teardown flag before flushing the work to prevent new work + * from being scheduled while we are cleaning up. + */ + spin_lock_irqsave(&gadget->state_lock, flags); + gadget->teardown =3D true; + spin_unlock_irqrestore(&gadget->state_lock, flags); flush_work(&gadget->work); ida_free(&gadget_id_numbers, gadget->id_number); cancel_work_sync(&udc->vbus_work); diff --git a/include/linux/usb/gadget.h b/include/linux/usb/gadget.h index 0f28c5512fcb..8b5e593f7966 100644 --- a/include/linux/usb/gadget.h +++ b/include/linux/usb/gadget.h @@ -351,6 +351,9 @@ struct usb_gadget_ops { * can handle. The UDC must support this and all slower speeds and lower * number of lanes. * @state: the state we are now (attached, suspended, configured, etc) + * @state_lock: Spinlock protecting the `state` and `teardown` members. + * @teardown: True if the device is undergoing teardown, used to prevent + * new work from being scheduled during cleanup. * @name: Identifies the controller hardware type. Used in diagnostics * and sometimes configuration. * @dev: Driver model state for this abstract device. @@ -426,6 +429,8 @@ struct usb_gadget { enum usb_ssp_rate max_ssp_rate; =20 enum usb_device_state state; + spinlock_t state_lock; + bool teardown; const char *name; struct device dev; unsigned isoch_delay; --=20 2.51.0.760.g7b8bcc2412-goog