Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756111Ab0GHKmo (ORCPT ); Thu, 8 Jul 2010 06:42:44 -0400 Received: from e28smtp04.in.ibm.com ([122.248.162.4]:59862 "EHLO e28smtp04.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752613Ab0GHKmm (ORCPT ); Thu, 8 Jul 2010 06:42:42 -0400 From: "Aneesh Kumar K. V" To: Nick Piggin Cc: hch@infradead.org, viro@zeniv.linux.org.uk, adilger@sun.com, corbet@lwn.net, serue@us.ibm.com, neilb@suse.de, hooanon05@yahoo.co.jp, bfields@fieldses.org, linux-fsdevel@vger.kernel.org, sfrench@us.ibm.com, philippe.deniel@CEA.FR, linux-kernel@vger.kernel.org Subject: Re: [PATCH -V14 04/11] vfs: Allow handle based open on symlinks In-Reply-To: <20100707164859.GB9263@laptop> References: <1276621981-2774-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1276621981-2774-5-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <20100707164859.GB9263@laptop> User-Agent: Notmuch/ (http://notmuchmail.org) Emacs/24.0.50.1 (i686-pc-linux-gnu) Date: Thu, 08 Jul 2010 16:12:36 +0530 Message-ID: <87tyoadzkz.fsf@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4088 Lines: 126 On Thu, 8 Jul 2010 02:48:59 +1000, Nick Piggin wrote: > On Tue, Jun 15, 2010 at 10:42:54PM +0530, Aneesh Kumar K.V wrote: > > The patch update may_open to allow handle based open on symlinks. > > The file handle based API use file descritor returned from open_by_handle_at > > to do different file system operations. To find the link target name we > > need to get a file descriptor on symlinks. > > > > Signed-off-by: Aneesh Kumar K.V > > --- > > fs/namei.c | 17 ++++++++++++++--- > > 1 files changed, 14 insertions(+), 3 deletions(-) > > > > diff --git a/fs/namei.c b/fs/namei.c > > index c2d19c7..417bf53 100644 > > --- a/fs/namei.c > > +++ b/fs/namei.c > > @@ -1422,7 +1422,7 @@ int vfs_create(struct inode *dir, struct dentry *dentry, int mode, > > return error; > > } > > > > -int may_open(struct path *path, int acc_mode, int flag) > > +static int __may_open(struct path *path, int acc_mode, int flag, int handle) > > { > > struct dentry *dentry = path->dentry; > > struct inode *inode = dentry->d_inode; > > @@ -1433,7 +1433,13 @@ int may_open(struct path *path, int acc_mode, int flag) > > > > switch (inode->i_mode & S_IFMT) { > > case S_IFLNK: > > - return -ELOOP; > > + /* > > + * For file handle based open we should allow > > + * open of symlink. > > + */ > > + if (!handle) > > + return -ELOOP; > > + break; > > case S_IFDIR: > > if (acc_mode & MAY_WRITE) > > return -EISDIR; > > @@ -1473,6 +1479,11 @@ int may_open(struct path *path, int acc_mode, int flag) > > return break_lease(inode, flag); > > } > > > > +int may_open(struct path *path, int acc_mode, int flag) > > +{ > > + return __may_open(path, acc_mode, flag, 0); > > +} > > Why don't you just add MAY_OPEN_LNK instead of this ugliness? > Something like the below ? commit 69787f5ed6c8a7a63ad21ef5d7de0b62f124ff0a Author: Aneesh Kumar K.V Date: Tue Jul 6 23:25:57 2010 +0530 vfs: Allow handle based open on symlinks The patch update may_open to allow handle based open on symlinks. The file handle based API use file descritor returned from open_by_handle_at to do different file system operations. To find the link target name we need to get a file descriptor on symlinks. Signed-off-by: Aneesh Kumar K.V diff --git a/fs/namei.c b/fs/namei.c index de40312..2ea5c79 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1456,7 +1456,15 @@ int may_open(struct path *path, int acc_mode, int flag) switch (inode->i_mode & S_IFMT) { case S_IFLNK: - return -ELOOP; + /* + * Allow only if acc_mode contain + * open link request and read request. + */ + if (acc_mode != (MAY_OPEN_LINK | MAY_READ)) + return -ELOOP; + if (flag != O_RDONLY) + return -ELOOP; + break; case S_IFDIR: if (acc_mode & MAY_WRITE) return -EISDIR; diff --git a/fs/open.c b/fs/open.c index daf2534..a58837a 100644 --- a/fs/open.c +++ b/fs/open.c @@ -1266,8 +1266,15 @@ static long do_sys_open_by_handle(int mountdirfd, */ if (open_flag & __O_SYNC) open_flag |= O_DSYNC; + /* + * Handle based API allow open on a symlink + */ + if (S_ISLNK(path->dentry->d_inode->i_mode)) + acc_mode = MAY_OPEN_LINK; + else + acc_mode = MAY_OPEN; - acc_mode = MAY_OPEN | ACC_MODE(open_flag); + acc_mode |= ACC_MODE(open_flag); /* O_TRUNC implies we need access checks for write permissions */ if (open_flag & O_TRUNC) diff --git a/include/linux/fs.h b/include/linux/fs.h index cbff4ca..eaf13d1 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -53,6 +53,7 @@ struct inodes_stat_t { #define MAY_APPEND 8 #define MAY_ACCESS 16 #define MAY_OPEN 32 +#define MAY_OPEN_LINK 64 /* * flags in file.f_mode. Note that FMODE_READ and FMODE_WRITE must correspond -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/