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Subject[PATCH 25/35] VFS: Create user_path_nd() to lookup both parent and target
Date
Proof-of-concept implementation of user_path_nd().  Lookup both the
parent and the target of a user-supplied filename, to supply later to
union copyup routines.
---
fs/namei.c | 31 +++++++++++++++++++++++++++++++
include/linux/namei.h | 2 ++
2 files changed, 33 insertions(+), 0 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c
index 24e0cb2..68aa8ab 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1563,6 +1563,37 @@ static int user_path_parent(int dfd, const char __user *path,
return error;
}

+int user_path_nd(int dfd, const char __user *filename,
+ unsigned flags, struct nameidata *parent_nd,
+ struct path *child, char **tmp)
+{
+ struct nameidata child_nd;
+ char *s = getname(filename);
+ int error;
+
+ if (IS_ERR(s))
+ return PTR_ERR(s);
+
+ /* Lookup parent */
+ error = do_path_lookup(dfd, s, LOOKUP_PARENT, parent_nd);
+ if (error)
+ goto out_putname;
+
+ /* Lookup child - XXX optimize, racy */
+ error = do_path_lookup(dfd, s, flags, &child_nd);
+ if (error)
+ goto out_path_put;
+ *child = child_nd.path;
+ *tmp = s;
+ return 0;
+
+out_path_put:
+ path_put(&parent_nd->path);
+out_putname:
+ putname(s);
+ return error;
+}
+
/*
* It's inline, so penalty for filesystems that don't use sticky bit is
* minimal.
diff --git a/include/linux/namei.h b/include/linux/namei.h
index 05b441d..83dc8b5 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -58,6 +58,8 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT, LAST_BIND};
#define LOOKUP_RENAME_TARGET 0x0800

extern int user_path_at(int, const char __user *, unsigned, struct path *);
+extern int user_path_nd(int, const char __user *, unsigned,
+ struct nameidata *, struct path *, char **);

#define user_path(name, path) user_path_at(AT_FDCWD, name, LOOKUP_FOLLOW, path)
#define user_lpath(name, path) user_path_at(AT_FDCWD, name, 0, path)
--
1.6.3.3


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