kernfs: associate a new kernfs_node with its parent on creation
Once created, a kernfs_node is always destroyed by kernfs_put().
Since ba7443bc656e ("sysfs, kernfs: implement
kernfs_create/destroy_root()"), kernfs_put() depends on kernfs_root()
to locate the ino_ida. kernfs_root() in turn depends on
kernfs_node->parent being set for !dir nodes. This means that
kernfs_put() of a !dir node requires its ->parent to be initialized.
This leads to oops when a newly created !dir node is destroyed without
going through kernfs_add_one() or after failing kernfs_add_one()
before ->parent is set. kernfs_root() invoked from kernfs_put() will
try to dereference NULL parent.
Fix it by moving parent association to kernfs_new_node() from
kernfs_add_one(). kernfs_new_node() now takes @parent instead of
@root and determines the root from the parent and also sets the new
node's parent properly. @parent parameter is removed from
kernfs_add_one(). As there's no parent when creating the root node,
__kernfs_new_node() which takes @root as before and doesn't set the
parent is used in that case.
This ensures that a kernfs_node in any stage in its life has its
parent associated and thus can be put.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index bdd3885..dbf397b 100644
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -829,8 +829,7 @@
if (name_is_static)
flags |= KERNFS_STATIC_NAME;
- kn = kernfs_new_node(kernfs_root(parent), name,
- (mode & S_IALLUGO) | S_IFREG, flags);
+ kn = kernfs_new_node(parent, name, (mode & S_IALLUGO) | S_IFREG, flags);
if (!kn)
return ERR_PTR(-ENOMEM);
@@ -857,7 +856,7 @@
kn->flags |= KERNFS_HAS_MMAP;
kernfs_addrm_start(&acxt);
- rc = kernfs_add_one(&acxt, kn, parent);
+ rc = kernfs_add_one(&acxt, kn);
kernfs_addrm_finish(&acxt);
if (rc) {