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kernfs: add REMOVED check to create and rename paths

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kernfs currently assumes that the caller doesn't try to create a new
node under a removed parent, rename a removed node, or move a node
under a removed node.  While this works fine for sysfs, it'd be nice
to have protection against such cases especially given that kernfs is
planned to add support for mkdir, rmdir and rename requsts from
userland which may make race conditions more likely.

This patch updates create and rename paths to check REMOVED and fail
the operation with -ENOENT if performed on or towards removed nodes.
Note that remove path already has such check.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Tejun Heo 2013-12-11 16:02:56 -05:00 committed by Greg Kroah-Hartman
parent bb8b9d095c
commit d0ae3d4347
1 changed files with 7 additions and 0 deletions
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7
fs/kernfs/dir.c
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@ -430,6 +430,9 @@ int kernfs_add_one(struct kernfs_addrm_cxt *acxt, struct kernfs_node *kn,
if (kernfs_type(parent) != KERNFS_DIR)
return -EINVAL;
if (parent->flags & KERNFS_REMOVED)
return -ENOENT;
kn->hash = kernfs_name_hash(kn->name, kn->ns);
kn->parent = parent;
kernfs_get(parent);
@ -863,6 +866,10 @@ int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
mutex_lock(&kernfs_mutex);
error = -ENOENT;
if ((kn->flags | new_parent->flags) & KERNFS_REMOVED)
goto out;
error = 0;
if ((kn->parent == new_parent) && (kn->ns == new_ns) &&
(strcmp(kn->name, new_name) == 0))