From mboxrd@z Thu Jan 1 00:00:00 1970 From: Valerie Aurora Subject: [PATCH 2/4] VFS: create user_path_and_parent() Date: Tue, 30 Mar 2010 14:16:55 -0700 Message-ID: <1269983817-3252-3-git-send-email-vaurora@redhat.com> References: <1269983817-3252-1-git-send-email-vaurora@redhat.com> <1269983817-3252-2-git-send-email-vaurora@redhat.com> Cc: linux-fsdevel@vger.kernel.org To: Alexander Viro Return-path: Received: from mx1.redhat.com ([209.132.183.28]:39717 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753703Ab0C3VRi (ORCPT ); Tue, 30 Mar 2010 17:17:38 -0400 In-Reply-To: <1269983817-3252-2-git-send-email-vaurora@redhat.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: 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