[PATCH] Fix null pointer dereference caused by sysfs_notify on binary attribute

[Nick Dyer]

It would be nice to have this work as expected but for now this is a minimal
fix to prevent the kernel panic.

Signed-off-by: Nick Dyer <nick.dyer@xxxxxxxxxxx>
---
 fs/sysfs/file.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index 602f56d..976819b 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 (sd->s_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);
-- 
1.7.10.4

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