From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 832E4C3A5A1 for ; Thu, 22 Aug 2019 17:09:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 574112341E for ; Thu, 22 Aug 2019 17:09:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1566493759; bh=BceQIvYA6h6G5G9kleh1h72iqWj3mord1EgIKK2cbS4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=yGVmfYmhzDY6Gio3YEUWvSn0cKjT2ukIRQOlMuohjylAqPhI+3Qb/PvamLw8vLaff T4DnS63AkE6HhKFKGpUyWxSpSsrvGSeOB7ULLnkCia212qtJOKVRfZZVSvgh+p7V32 /UYnHIn2llolfSVrANJFhCBEMp2nAibsHZMHNL4M= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390724AbfHVRJS (ORCPT ); Thu, 22 Aug 2019 13:09:18 -0400 Received: from mail.kernel.org ([198.145.29.99]:59282 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390662AbfHVRJG (ORCPT ); Thu, 22 Aug 2019 13:09:06 -0400 Received: from sasha-vm.mshome.net (wsip-184-188-36-2.sd.sd.cox.net [184.188.36.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 0262F233FD; Thu, 22 Aug 2019 17:09:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1566493746; bh=BceQIvYA6h6G5G9kleh1h72iqWj3mord1EgIKK2cbS4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ien4CO5oIek2jrmauRld0Z72feE0zfOcP+CCXE8S1y2fsfjAsEQd6y6zwVrknDr1g tB7T0ZE/W3y0Sqd4d9gyVfWOXW6sHohIbgcOtsIdeR6vnehNIuiHu4SkDlgDXnLdhR 3YAwGoXal/YwcPn1X6Ax8X3CRUmjc9hwgR4N9qTk= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Alan Stern , syzbot+30cf45ebfe0b0c4847a1@syzkaller.appspotmail.com, Greg Kroah-Hartman Subject: [PATCH 5.2 095/135] USB: core: Fix races in character device registration and deregistraion Date: Thu, 22 Aug 2019 13:07:31 -0400 Message-Id: <20190822170811.13303-96-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190822170811.13303-1-sashal@kernel.org> References: <20190822170811.13303-1-sashal@kernel.org> MIME-Version: 1.0 X-KernelTest-Patch: http://kernel.org/pub/linux/kernel/v5.x/stable-review/patch-5.2.10-rc1.gz X-KernelTest-Tree: git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git X-KernelTest-Branch: linux-5.2.y X-KernelTest-Patches: git://git.kernel.org/pub/scm/linux/kernel/git/stable/stable-queue.git X-KernelTest-Version: 5.2.10-rc1 X-KernelTest-Deadline: 2019-08-24T17:07+00:00 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Alan Stern commit 303911cfc5b95d33687d9046133ff184cf5043ff upstream. The syzbot fuzzer has found two (!) races in the USB character device registration and deregistration routines. This patch fixes the races. The first race results from the fact that usb_deregister_dev() sets usb_minors[intf->minor] to NULL before calling device_destroy() on the class device. This leaves a window during which another thread can allocate the same minor number but will encounter a duplicate name error when it tries to register its own class device. A typical error message in the system log would look like: sysfs: cannot create duplicate filename '/class/usbmisc/ldusb0' The patch fixes this race by destroying the class device first. The second race is in usb_register_dev(). When that routine runs, it first allocates a minor number, then drops minor_rwsem, and then creates the class device. If the device creation fails, the minor number is deallocated and the whole routine returns an error. But during the time while minor_rwsem was dropped, there is a window in which the minor number is allocated and so another thread can successfully open the device file. Typically this results in use-after-free errors or invalid accesses when the other thread closes its open file reference, because the kernel then tries to release resources that were already deallocated when usb_register_dev() failed. The patch fixes this race by keeping minor_rwsem locked throughout the entire routine. Reported-and-tested-by: syzbot+30cf45ebfe0b0c4847a1@syzkaller.appspotmail.com Signed-off-by: Alan Stern CC: Link: https://lore.kernel.org/r/Pine.LNX.4.44L0.1908121607590.1659-100000@iolanthe.rowland.org Signed-off-by: Greg Kroah-Hartman --- drivers/usb/core/file.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/drivers/usb/core/file.c b/drivers/usb/core/file.c index 65de6f73b6725..558890ada0e5b 100644 --- a/drivers/usb/core/file.c +++ b/drivers/usb/core/file.c @@ -193,9 +193,10 @@ int usb_register_dev(struct usb_interface *intf, intf->minor = minor; break; } - up_write(&minor_rwsem); - if (intf->minor < 0) + if (intf->minor < 0) { + up_write(&minor_rwsem); return -EXFULL; + } /* create a usb class device for this usb interface */ snprintf(name, sizeof(name), class_driver->name, minor - minor_base); @@ -203,12 +204,11 @@ int usb_register_dev(struct usb_interface *intf, MKDEV(USB_MAJOR, minor), class_driver, "%s", kbasename(name)); if (IS_ERR(intf->usb_dev)) { - down_write(&minor_rwsem); usb_minors[minor] = NULL; intf->minor = -1; - up_write(&minor_rwsem); retval = PTR_ERR(intf->usb_dev); } + up_write(&minor_rwsem); return retval; } EXPORT_SYMBOL_GPL(usb_register_dev); @@ -234,12 +234,12 @@ void usb_deregister_dev(struct usb_interface *intf, return; dev_dbg(&intf->dev, "removing %d minor\n", intf->minor); + device_destroy(usb_class->class, MKDEV(USB_MAJOR, intf->minor)); down_write(&minor_rwsem); usb_minors[intf->minor] = NULL; up_write(&minor_rwsem); - device_destroy(usb_class->class, MKDEV(USB_MAJOR, intf->minor)); intf->usb_dev = NULL; intf->minor = -1; destroy_usb_class(); -- 2.20.1