Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S936310Ab3DQRil (ORCPT ); Wed, 17 Apr 2013 13:38:41 -0400 Received: from mx1.redhat.com ([209.132.183.28]:7906 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752272Ab3DQRik (ORCPT ); Wed, 17 Apr 2013 13:38:40 -0400 From: Benjamin Tissoires To: Jiri Kosina , Dmitry Torokhov , Benjamin Tissoires , linux-input@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Benjamin Tissoires Subject: [PATCH 3/4] HID: debug: empty output queue on read Date: Wed, 17 Apr 2013 19:38:15 +0200 Message-Id: <1366220296-14346-4-git-send-email-benjamin.tissoires@redhat.com> In-Reply-To: <1366220296-14346-1-git-send-email-benjamin.tissoires@redhat.com> References: <1366220296-14346-1-git-send-email-benjamin.tissoires@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2192 Lines: 72 If an event occurs while the hid debugfs is forwarding events, list->tail is updated during copy_to_user(). Remove the gotos and use a regular while-loop to empty the queue. Second benefit, it checks that we are not writing more than count bytes to the user-space output buffer. Signed-off-by: Benjamin Tissoires --- drivers/hid/hid-debug.c | 27 +++++++++++---------------- 1 file changed, 11 insertions(+), 16 deletions(-) diff --git a/drivers/hid/hid-debug.c b/drivers/hid/hid-debug.c index 094cbcf..1dc8104 100644 --- a/drivers/hid/hid-debug.c +++ b/drivers/hid/hid-debug.c @@ -1000,6 +1000,7 @@ static ssize_t hid_debug_events_read(struct file *file, char __user *buffer, size_t count, loff_t *ppos) { struct hid_debug_list *list = file->private_data; + char *buf_head; int ret = 0, len; DECLARE_WAITQUEUE(wait, current); @@ -1039,28 +1040,22 @@ static ssize_t hid_debug_events_read(struct file *file, char __user *buffer, goto out; /* pass the ringbuffer contents to userspace */ -copy_rest: - if (list->tail == list->head) - goto out; - if (list->tail > list->head) { - len = list->tail - list->head; + while (list->tail != list->head && ret < count) { + buf_head = &list->hid_debug_buf[list->head]; - if (copy_to_user(buffer + ret, &list->hid_debug_buf[list->head], len)) { - ret = -EFAULT; - goto out; - } - ret += len; - list->head += len; - } else { - len = HID_DEBUG_BUFSIZE - list->head; + if (list->tail > list->head) + len = list->tail - list->head; + else + len = HID_DEBUG_BUFSIZE - list->head; + + len = min(count - ret, len); - if (copy_to_user(buffer, &list->hid_debug_buf[list->head], len)) { + if (copy_to_user(buffer + ret, buf_head, len)) { ret = -EFAULT; goto out; } - list->head = 0; ret += len; - goto copy_rest; + list->head = (list->head + len) % HID_DEBUG_BUFSIZE; } } -- 1.8.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/