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inotify: Ensure we alwasy write the terminating NULL.

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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 <ebiederm@aristanetworks.com>
Signed-off-by: Eric Paris <eparis@redhat.com>
This commit is contained in:
Eric W. Biederman 2009-08-27 03:20:04 -07:00 committed by Eric Paris
parent dead537dd8
commit 0db501bd06
1 changed files with 6 additions and 7 deletions
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13
fs/notify/inotify/inotify_user.c
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@ -47,9 +47,6 @@
static struct vfsmount *inotify_mnt __read_mostly; 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/ */ /* these are configurable via /proc/sys/fs/inotify/ */
static int inotify_max_user_instances __read_mostly; static int inotify_max_user_instances __read_mostly;
static int inotify_max_queued_events __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); inotify_free_event_priv(fsn_priv);
} }
/* round up event->name_len so it is a multiple of event_size */ /* round up event->name_len so it is a multiple of event_size
name_len = roundup(event->name_len, 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.len = name_len;
inotify_event.mask = inotify_mask_to_arg(event->mask); 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; return -EFAULT;
buf += event->name_len; buf += event->name_len;
/* fill userspace with 0's from nul_inotify_event */ /* fill userspace with 0's */
if (copy_to_user(buf, &nul_inotify_event, len_to_zero)) if (clear_user(buf, len_to_zero))
return -EFAULT; return -EFAULT;
buf += len_to_zero; buf += len_to_zero;
event_size += name_len; event_size += name_len;