3 files changed, 28 insertions, 14 deletions

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 78f3403300af..ac127cd008bf 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -232,9 +232,6 @@ static int kernfs_link_sibling(struct kernfs_node *kn)
         struct rb_node **node = &kn->parent->dir.children.rb_node;
         struct rb_node *parent = NULL;
 
-        if (kernfs_type(kn) == KERNFS_DIR)
-                kn->parent->dir.subdirs++;
-
         while (*node) {
                 struct kernfs_node *pos;
                 int result;
@@ -249,9 +246,15 @@ static int kernfs_link_sibling(struct kernfs_node *kn)
                 else
                         return -EEXIST;
         }
+
         /* add new node and rebalance the tree */
         rb_link_node(&kn->rb, parent, node);
         rb_insert_color(&kn->rb, &kn->parent->dir.children);
+
+        /* successfully added, account subdir number */
+        if (kernfs_type(kn) == KERNFS_DIR)
+                kn->parent->dir.subdirs++;
+
         return 0;
 }
 
diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index 8034706a7af8..5e9a80cfc3d8 100644
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -484,6 +484,8 @@ static int kernfs_fop_mmap(struct file *file, struct vm_area_struct *vma)
 
         ops = kernfs_ops(of->kn);
         rc = ops->mmap(of, vma);
+        if (rc)
+                goto out_put;
 
         /*
          * PowerPC's pci_mmap of legacy_mem uses shmem_zero_setup()
@@ -608,6 +610,7 @@ static void kernfs_put_open_node(struct kernfs_node *kn,
 static int kernfs_fop_open(struct inode *inode, struct file *file)
 {
         struct kernfs_node *kn = file->f_path.dentry->d_fsdata;
+        struct kernfs_root *root = kernfs_root(kn);
         const struct kernfs_ops *ops;
         struct kernfs_open_file *of;
         bool has_read, has_write, has_mmap;
@@ -622,14 +625,16 @@ static int kernfs_fop_open(struct inode *inode, struct file *file)
         has_write = ops->write || ops->mmap;
         has_mmap = ops->mmap;
 
-        /* check perms and supported operations */
-        if ((file->f_mode & FMODE_WRITE) &&
-            (!(inode->i_mode & S_IWUGO) || !has_write))
-                goto err_out;
+        /* see the flag definition for details */
+        if (root->flags & KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK) {
+                if ((file->f_mode & FMODE_WRITE) &&
+                    (!(inode->i_mode & S_IWUGO) || !has_write))
+                        goto err_out;
 
-        if ((file->f_mode & FMODE_READ) &&
-            (!(inode->i_mode & S_IRUGO) || !has_read))
-                goto err_out;
+                if ((file->f_mode & FMODE_READ) &&
+                    (!(inode->i_mode & S_IRUGO) || !has_read))
+                        goto err_out;
+        }
 
         /* allocate a kernfs_open_file for the file */
         error = -ENOMEM;
diff --git a/fs/kernfs/inode.c b/fs/kernfs/inode.c
index abb0f1f53d93..985217626e66 100644
--- a/fs/kernfs/inode.c
+++ b/fs/kernfs/inode.c
@@ -48,14 +48,18 @@ void __init kernfs_inode_init(void)
 
 static struct kernfs_iattrs *kernfs_iattrs(struct kernfs_node *kn)
 {
+        static DEFINE_MUTEX(iattr_mutex);
+        struct kernfs_iattrs *ret;
         struct iattr *iattrs;
 
+        mutex_lock(&iattr_mutex);
+
         if (kn->iattr)
-                return kn->iattr;
+                goto out_unlock;
 
         kn->iattr = kzalloc(sizeof(struct kernfs_iattrs), GFP_KERNEL);
         if (!kn->iattr)
-                return NULL;
+                goto out_unlock;
         iattrs = &kn->iattr->ia_iattr;
 
         /* assign default attributes */
@@ -65,8 +69,10 @@ static struct kernfs_iattrs *kernfs_iattrs(struct kernfs_node *kn)
         iattrs->ia_atime = iattrs->ia_mtime = iattrs->ia_ctime = CURRENT_TIME;
 
         simple_xattrs_init(&kn->iattr->xattrs);
-
-        return kn->iattr;
+out_unlock:
+        ret = kn->iattr;
+        mutex_unlock(&iattr_mutex);
+        return ret;
 }
 
 static int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)