sysfs_notify is only possible on file attributes

If sysfs_notify is called on a binary attribute, bad things can
happen, so prevent it.

Note, no in-kernel usage of this is currently present, but in the
future, it's good to be safe.

Changes in V2:
- Also ignore sysfs_notify on dirs, links
- Use WARN_ON rather than silently failing
- Compiled and tested (huge apologies about first submission)

Signed-off-by: Nick Dyer <nick.dyer@itdev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 6 insertions, 4 deletions

diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index 602f56db0442..d2bb7ed8fa74 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -449,10 +449,12 @@ void sysfs_notify_dirent(struct sysfs_dirent *sd)
 
         spin_lock_irqsave(&sysfs_open_dirent_lock, flags);
 
-        od = sd->s_attr.open;
-        if (od) {
-                atomic_inc(&od->event);
-                wake_up_interruptible(&od->poll);
+        if (!WARN_ON(sysfs_type(sd) != SYSFS_KOBJ_ATTR)) {
+                od = sd->s_attr.open;
+                if (od) {
+                        atomic_inc(&od->event);
+                        wake_up_interruptible(&od->poll);
+                }
         }
 
         spin_unlock_irqrestore(&sysfs_open_dirent_lock, flags);