From patchwork Fri Oct 18 14:17:50 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Johan Hovold X-Patchwork-Id: 11198587 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 74A701599 for ; Fri, 18 Oct 2019 14:18:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5679C222C5 for ; Fri, 18 Oct 2019 14:18:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1571408333; bh=GY9sgDJVxMpUl2IAi08bvJ70wUz6JavTXmmFwL7vT6k=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=s1OE426JW5/PqeH006woW64Vsy6DPor+MSr92htFHZr9jOMo/s87JmP4m5n3b56rH vJ0FCHhyDzeVWg8+fKbvtY4VqCs68e7GG4cRXRiG733a7pM+gSFAfu4dW50KpYNOjf sjHwU2QoF6i7W+MzyFdjzol8BXkB9oB2gUN207kw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2442885AbfJROSl (ORCPT ); Fri, 18 Oct 2019 10:18:41 -0400 Received: from mail-lj1-f194.google.com ([209.85.208.194]:44840 "EHLO mail-lj1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732676AbfJROSk (ORCPT ); Fri, 18 Oct 2019 10:18:40 -0400 Received: by mail-lj1-f194.google.com with SMTP id m13so6385824ljj.11; Fri, 18 Oct 2019 07:18:38 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=lK62GsaMPQOlyqa+AeKYuWxGPH9VRYmA+fAbIM8QXgg=; b=UNMMwzrk7l/zo+MYQg8qxs0W8w+SoRYxOpfAT493SwFYcLSyACYWSDQzxjiBRSt8qY +pE7IXhgGFUrN4fDEna2IW7CNxmz0fDwt/wWx5Qzd0F9vV3aRlzZxvsiwdX64RCIJtr9 a5C6G+zhvFNIwoWvEM5T9CJTVHErlTSMQaXFaCCLWgHRlupg8vKwSZ7ViDXEFzkLDIeO 9HoExPgMa2Zq0Yj/bjsb/gz3B6yyyWQVnh8REXnSKx4TsQNZoMGVthhC86MKvUwFucCR LbK6S4wwszjpPyzvQpXDI40x3K7lXVMzFj5cYvwIv8uI3Q+y0CsRlw9Zs0FJ2shBAX+G voKw== X-Gm-Message-State: APjAAAW6Z05oqDPCmq7ml0vfN7g3hMGhP+EU82gcy3D+ZsKUPSNrfwbu kYDEfiCK2L08AqKaMVjHAfI= X-Google-Smtp-Source: APXvYqyT+4O2YoCKFj1gH2GwxW0feEY6wE3RN9nro6b0WUC13Xddq6uNuukLGSswJDT8hLZUJpCl6Q== X-Received: by 2002:a2e:86cd:: with SMTP id n13mr6579303ljj.252.1571408318149; Fri, 18 Oct 2019 07:18:38 -0700 (PDT) Received: from xi.terra (c-51f1e055.07-184-6d6c6d4.bbcust.telenor.se. [85.224.241.81]) by smtp.gmail.com with ESMTPSA id z26sm2202097lji.79.2019.10.18.07.18.36 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 18 Oct 2019 07:18:36 -0700 (PDT) Received: from johan by xi.terra with local (Exim 4.92.2) (envelope-from ) id 1iLT5d-0006CE-9Q; Fri, 18 Oct 2019 16:18:49 +0200 From: Johan Hovold To: Greg Kroah-Hartman Cc: Alan Stern , Oliver Neukum , "Paul E . McKenney" , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, Johan Hovold , stable Subject: [PATCH RFC 2/2] USB: ldusb: fix ring-buffer locking Date: Fri, 18 Oct 2019 16:17:50 +0200 Message-Id: <20191018141750.23756-3-johan@kernel.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20191018141750.23756-1-johan@kernel.org> References: <20191018141750.23756-1-johan@kernel.org> MIME-Version: 1.0 Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org The custom ring-buffer implementation was merged without any locking whatsoever, but a spinlock was later added by commit 9d33efd9a791 ("USB: ldusb bugfix"). The lock did not cover the loads from the ring-buffer-entry after determining the buffer was non-empty, nor the update of the tail index once the entry had been processed. The former could lead to stale data being returned, while the latter could lead to memory corruption on sufficiently weakly ordered architectures. Fixes: 2824bd250f0b ("[PATCH] USB: add ldusb driver") Fixes: 9d33efd9a791 ("USB: ldusb bugfix") Cc: stable # 2.6.13 Signed-off-by: Johan Hovold --- drivers/usb/misc/ldusb.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/drivers/usb/misc/ldusb.c b/drivers/usb/misc/ldusb.c index 94780e14e95d..c6cf2fa6cf4c 100644 --- a/drivers/usb/misc/ldusb.c +++ b/drivers/usb/misc/ldusb.c @@ -477,11 +477,11 @@ static ssize_t ld_usb_read(struct file *file, char __user *buffer, size_t count, spin_lock_irq(&dev->rbsl); } - spin_unlock_irq(&dev->rbsl); /* actual_buffer contains actual_length + interrupt_in_buffer */ actual_buffer = (size_t *)(dev->ring_buffer + dev->ring_tail * (sizeof(size_t)+dev->interrupt_in_endpoint_size)); if (*actual_buffer > sizeof(size_t) + dev->interrupt_in_endpoint_size) { + spin_unlock_irq(&dev->rbsl); retval = -EIO; goto unlock_exit; } @@ -489,17 +489,26 @@ static ssize_t ld_usb_read(struct file *file, char __user *buffer, size_t count, if (bytes_to_read < *actual_buffer) dev_warn(&dev->intf->dev, "Read buffer overflow, %zd bytes dropped\n", *actual_buffer-bytes_to_read); + spin_unlock_irq(&dev->rbsl); + + /* + * Pairs with spin_unlock_irqrestore() in + * ld_usb_interrupt_in_callback() and makes sure the ring-buffer entry + * has been updated before copy_to_user(). + */ + smp_rmb(); /* copy one interrupt_in_buffer from ring_buffer into userspace */ if (copy_to_user(buffer, actual_buffer+1, bytes_to_read)) { retval = -EFAULT; goto unlock_exit; } - dev->ring_tail = (dev->ring_tail+1) % ring_buffer_size; - retval = bytes_to_read; spin_lock_irq(&dev->rbsl); + + dev->ring_tail = (dev->ring_tail + 1) % ring_buffer_size; + if (dev->buffer_overflow) { dev->buffer_overflow = 0; spin_unlock_irq(&dev->rbsl);