Proof-of-concept implementation of user_path_and_parent(). Lookup
both the parent and the target of a user-supplied filename, to supply
later to path_permission(). This is for union mounts, in which the
write permission of a file depends on the path used to access it.
---
fs/namei.c | 33 +++++++++++++++++++++++++++++++++
include/linux/namei.h | 2 ++
2 files changed, 35 insertions(+), 0 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c
index b4ba87d..b4b8594 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1577,6 +1577,39 @@ static int user_path_parent(int dfd, const char __user *path,
return error;
}
+int user_path_and_parent(int dfd, const char __user *filename,
+ unsigned flags, struct path *parent,
+ struct path *child)
+{
+ struct nameidata parent_nd;
+ 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;
+ *parent = parent_nd.path;
+
+ /* Lookup child - XXX optimize, racy */
+ error = do_path_lookup(dfd, s, flags, &child_nd);
+ if (error)
+ goto out_path_put;
+ *child = child_nd.path;
+ putname(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..1c81b17 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_and_parent(int , const char __user *, unsigned,
+ struct path *, struct path *);
#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
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
