vfs: define struct filename and have getname() return it

getname() is intended to copy pathname strings from userspace into a
kernel buffer. The result is just a string in kernel space. It would
however be quite helpful to be able to attach some ancillary info to
the string.

For instance, we could attach some audit-related info to reduce the
amount of audit-related processing needed. When auditing is enabled,
we could also call getname() on the string more than once and not
need to recopy it from userspace.

This patchset converts the getname()/putname() interfaces to return
a struct instead of a string. For now, the struct just tracks the
string in kernel space and the original userland pointer for it.

Later, we'll add other information to the struct as it becomes
convenient.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 11 insertions, 3 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index b44b4ca..6c93b46 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2196,6 +2196,10 @@ static inline int break_lease(struct inode *inode, unsigned int mode)
 #endif /* CONFIG_FILE_LOCKING */
 
 /* fs/open.c */
+struct filename {
+	const char *name;		/* pointer to actual string */
+	const __user char *uptr;	/* original userland pointer */
+};
 
 extern int do_truncate(struct dentry *, loff_t start, unsigned int time_attrs,
 		       struct file *filp);
@@ -2208,7 +2212,9 @@ extern struct file *file_open_root(struct dentry *, struct vfsmount *,
 				   const char *, int);
 extern struct file * dentry_open(const struct path *, int, const struct cred *);
 extern int filp_close(struct file *, fl_owner_t id);
-extern char * getname(const char __user *);
+
+extern struct filename *getname(const char __user *);
+
 enum {
 	FILE_CREATED = 1,
 	FILE_OPENED = 2
@@ -2228,12 +2234,14 @@ extern void __init vfs_caches_init(unsigned long);
 
 extern struct kmem_cache *names_cachep;
 
+extern void final_putname(struct filename *name);
+
 #define __getname()		kmem_cache_alloc(names_cachep, GFP_KERNEL)
 #define __putname(name)		kmem_cache_free(names_cachep, (void *)(name))
 #ifndef CONFIG_AUDITSYSCALL
-#define putname(name)   __putname(name)
+#define putname(name)		final_putname(name)
 #else
-extern void putname(const char *name);
+extern void putname(struct filename *name);
 #endif
 
 #ifdef CONFIG_BLOCK