From mboxrd@z Thu Jan 1 00:00:00 1970 From: ebiederm@xmission.com (Eric W. Biederman) Subject: [PATCH] inotify: Ensure we alwasy write the terminating NULL. Date: Thu, 27 Aug 2009 03:20:04 -0700 Message-ID: References: <1251299483.2308.32.camel@dhcp231-106.rdu.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, "Rafael J. Wysocki" To: Eric Paris Return-path: In-Reply-To: <1251299483.2308.32.camel@dhcp231-106.rdu.redhat.com> (Eric Paris's message of "Wed\, 26 Aug 2009 11\:11\:23 -0400") Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org Before the rewrite copy_event_to_user always wrote a terqminating '\0' byte to user space after the filename. Since the rewrite that terminating byte was skipped if your filename is exactly a multiple of event_size. Ouch! So add one byte to name_size before we round up and use clear_user to set userspace to zero like /dev/zero does instead of copying the strange nul_inotify_event. I can't quite convince myself len_to_zero will never exceed 16 and even if it doesn't clear_user should be more efficient and a more accurate reflection of what the code is trying to do. Signed-off-by: Eric W. Biederman --- fs/notify/inotify/inotify_user.c | 13 ++++++------- 1 files changed, 6 insertions(+), 7 deletions(-) diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c index f30d9bb..90ae8ad 100644 --- a/fs/notify/inotify/inotify_user.c +++ b/fs/notify/inotify/inotify_user.c @@ -47,9 +47,6 @@ static struct vfsmount *inotify_mnt __read_mostly; -/* this just sits here and wastes global memory. used to just pad userspace messages with zeros */ -static struct inotify_event nul_inotify_event; - /* these are configurable via /proc/sys/fs/inotify/ */ static int inotify_max_user_instances __read_mostly; static int inotify_max_queued_events __read_mostly; @@ -199,8 +196,10 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group, inotify_free_event_priv(fsn_priv); } - /* round up event->name_len so it is a multiple of event_size */ - name_len = roundup(event->name_len, event_size); + /* round up event->name_len so it is a multiple of event_size + * plus an extra byte for the terminating '\0'. + */ + name_len = roundup(event->name_len + 1, event_size); inotify_event.len = name_len; inotify_event.mask = inotify_mask_to_arg(event->mask); @@ -224,8 +223,8 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group, return -EFAULT; buf += event->name_len; - /* fill userspace with 0's from nul_inotify_event */ - if (copy_to_user(buf, &nul_inotify_event, len_to_zero)) + /* fill userspace with 0's */ + if (clear_user(buf, len_to_zero)) return -EFAULT; buf += len_to_zero; event_size += name_len; -- 1.6.2.5