ANDROID: sdcardfs: Check for NULL in revalidate

If the inode is in the process of being evicted,
the top value may be NULL.

Signed-off-by: Daniel Rosenberg <drosen@google.com>
Bug: 38502532
Change-Id: I0b9d04aab621e0398d44d1c5dc53293106aa5f89

fs/sdcardfs/dentry.c

@@ -109,14 +109,16 @@ static int sdcardfs_d_revalidate(struct dentry *dentry, unsigned int flags)
 		goto out;
 
 	/* If our top's inode is gone, we may be out of date */
-	inode = dentry->d_inode;
+	inode = igrab(dentry->d_inode);
 	if (inode) {
 		data = top_data_get(SDCARDFS_I(inode));
-		if (data->abandoned) {
+		if (!data || data->abandoned) {
 			d_drop(dentry);
 			err = 0;
 		}
+		if (data)
 			data_put(data);
+		iput(inode);
 	}
 
 out: