Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S967790Ab3DSBzv (ORCPT ); Thu, 18 Apr 2013 21:55:51 -0400 Received: from cantor2.suse.de ([195.135.220.15]:46026 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S967641Ab3DSBzt (ORCPT ); Thu, 18 Apr 2013 21:55:49 -0400 Date: Thu, 18 Apr 2013 18:55:47 -0700 (PDT) From: Jiri Kosina To: Benjamin Tissoires Cc: Dmitry Torokhov , Benjamin Tissoires , linux-input@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 3/4] HID: debug: empty output queue on read In-Reply-To: <1366220296-14346-4-git-send-email-benjamin.tissoires@redhat.com> Message-ID: References: <1366220296-14346-1-git-send-email-benjamin.tissoires@redhat.com> <1366220296-14346-4-git-send-email-benjamin.tissoires@redhat.com> User-Agent: Alpine 2.00 (LNX 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2277 Lines: 67 On Wed, 17 Apr 2013, Benjamin Tissoires wrote: > 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); This triggers a type checking warning in min(), and it seems to be correct on this one (mixing size_t with signed int). drivers/hid/hid-debug.c:1079: warning: comparison of distinct pointer types lacks a cast -- Jiri Kosina SUSE Labs -- 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/