From 3eef34ad7dc369b7183ec383908aff3da2f6e5ec Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Fri, 7 Feb 2014 13:32:07 -0500 Subject: kernfs: implement kernfs_get_parent(), kernfs_name/path() and friends kernfs_node->parent and ->name are currently marked as "published" indicating that kernfs users may access them directly; however, those fields may get updated by kernfs_rename[_ns]() and unrestricted access may lead to erroneous values or oops. Protect ->parent and ->name updates with a irq-safe spinlock kernfs_rename_lock and implement the following accessors for these fields. * kernfs_name() - format the node's name into the specified buffer * kernfs_path() - format the node's path into the specified buffer * pr_cont_kernfs_name() - pr_cont a node's name (doesn't need buffer) * pr_cont_kernfs_path() - pr_cont a node's path (doesn't need buffer) * kernfs_get_parent() - pin and return a node's parent All can be called under any context. The recursive sysfs_pathname() in fs/sysfs/dir.c is replaced with kernfs_path() and sysfs_rename_dir_ns() is updated to use kernfs_get_parent() instead of dereferencing parent directly. v2: Dummy definition of kernfs_path() for !CONFIG_KERNFS was missing static inline making it cause a lot of build warnings. Add it. Signed-off-by: Tejun Heo Signed-off-by: Greg Kroah-Hartman --- include/linux/kernfs.h | 26 +++++++++++++++++++++++++- 1 file changed, 25 insertions(+), 1 deletion(-) (limited to 'include/linux/kernfs.h') diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h index 9c899040c05e..8736ee86a1d6 100644 --- a/include/linux/kernfs.h +++ b/include/linux/kernfs.h @@ -91,7 +91,12 @@ struct kernfs_node { #ifdef CONFIG_DEBUG_LOCK_ALLOC struct lockdep_map dep_map; #endif - /* the following two fields are published */ + /* + * Use kernfs_get_parent() and kernfs_name/path() instead of + * accessing the following two fields directly. If the node is + * never moved to a different parent, it is safe to access the + * parent directly. + */ struct kernfs_node *parent; const char *name; @@ -229,6 +234,12 @@ static inline bool kernfs_ns_enabled(struct kernfs_node *kn) return kn->flags & KERNFS_NS; } +int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen); +char * __must_check kernfs_path(struct kernfs_node *kn, char *buf, + size_t buflen); +void pr_cont_kernfs_name(struct kernfs_node *kn); +void pr_cont_kernfs_path(struct kernfs_node *kn); +struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn); struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent, const char *name, const void *ns); void kernfs_get(struct kernfs_node *kn); @@ -283,6 +294,19 @@ static inline void kernfs_enable_ns(struct kernfs_node *kn) { } static inline bool kernfs_ns_enabled(struct kernfs_node *kn) { return false; } +static inline int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen) +{ return -ENOSYS; } + +static inline char * __must_check kernfs_path(struct kernfs_node *kn, char *buf, + size_t buflen) +{ return NULL; } + +static inline void pr_cont_kernfs_name(struct kernfs_node *kn) { } +static inline void pr_cont_kernfs_path(struct kernfs_node *kn) { } + +static inline struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn) +{ return NULL; } + static inline struct kernfs_node * kernfs_find_and_get_ns(struct kernfs_node *parent, const char *name, const void *ns) -- cgit v1.2.3