From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Howells Subject: [PATCH 6/6] Add an AT_NO_AUTOMOUNT flag to suppress terminal automount Date: Thu, 22 Jul 2010 18:59:13 +0100 Message-ID: <20100722175913.5552.3905.stgit@warthog.procyon.org.uk> References: <20100722175847.5552.11520.stgit@warthog.procyon.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Cc: linux-fsdevel@vger.kernel.org, linux-afs@lists.infradead.org, linux-nfs@vger.kernel.org, linux-cifs@vger.kernel.org, linux-kernel@vger.kernel.org, David Howells To: viro@ZenIV.linux.org.uk Return-path: In-Reply-To: <20100722175847.5552.11520.stgit@warthog.procyon.org.uk> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-cifs.vger.kernel.org Add an AT_NO_AUTOMOUNT flag to suppress terminal automounting of directories with follow_link semantics. This can be used by fstatat()/xstat() users to permit the gathering of attributes on an automount point and also prevent mass-automounting of a directory of automount points by ls. Signed-off-by: David Howells --- fs/namei.c | 15 ++++++++++----- fs/stat.c | 4 +++- include/linux/fcntl.h | 1 + include/linux/namei.h | 2 ++ 4 files changed, 16 insertions(+), 6 deletions(-) diff --git a/fs/namei.c b/fs/namei.c index 86068a2..056427e 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -654,7 +654,8 @@ static int follow_automount(struct path *path, int res) /* no need for dcache_lock, as serialization is taken care in * namespace.c */ -static int __follow_mount(struct path *path, unsigned nofollow) +static int __follow_mount(struct path *path, unsigned nofollow, + struct nameidata *nd) { struct vfsmount *mounted; int ret, res = 0; @@ -674,8 +675,12 @@ static int __follow_mount(struct path *path, unsigned nofollow) } if (!d_automount_point(path->dentry)) break; - if (nofollow) - return -ELOOP; + if (!(nd->flags & LOOKUP_CONTINUE)) { + if (nofollow) + return -ELOOP; + if (nd->flags & LOOKUP_NO_AUTOMOUNT) + break; + } ret = follow_automount(path, res); if (ret < 0) return ret; @@ -769,7 +774,7 @@ static int do_lookup(struct nameidata *nd, struct qstr *name, done: path->mnt = mnt; path->dentry = dentry; - ret = __follow_mount(path, 0); + ret = __follow_mount(path, 0, nd); if (unlikely(ret < 0)) path_put(path); return ret; @@ -1762,7 +1767,7 @@ static struct file *do_last(struct nameidata *nd, struct path *path, if (open_flag & O_EXCL) goto exit_dput; - error = __follow_mount(path, open_flag & O_NOFOLLOW); + error = __follow_mount(path, open_flag & O_NOFOLLOW, nd); if (error < 0) goto exit_dput; diff --git a/fs/stat.c b/fs/stat.c index c4ecd52..e4662de 100644 --- a/fs/stat.c +++ b/fs/stat.c @@ -74,11 +74,13 @@ int vfs_fstatat(int dfd, char __user *filename, struct kstat *stat, int flag) int error = -EINVAL; int lookup_flags = 0; - if ((flag & ~AT_SYMLINK_NOFOLLOW) != 0) + if ((flag & ~AT_SYMLINK_NOFOLLOW | AT_NO_AUTOMOUNT) != 0) goto out; if (!(flag & AT_SYMLINK_NOFOLLOW)) lookup_flags |= LOOKUP_FOLLOW; + if (flag & AT_NO_AUTOMOUNT) + lookup_flags |= LOOKUP_NO_AUTOMOUNT; error = user_path_at(dfd, filename, lookup_flags, &path); if (error) diff --git a/include/linux/fcntl.h b/include/linux/fcntl.h index afc00af..a562fa5 100644 --- a/include/linux/fcntl.h +++ b/include/linux/fcntl.h @@ -45,6 +45,7 @@ #define AT_REMOVEDIR 0x200 /* Remove directory instead of unlinking file. */ #define AT_SYMLINK_FOLLOW 0x400 /* Follow symbolic links. */ +#define AT_NO_AUTOMOUNT 0x800 /* Suppress terminal automount traversal */ #ifdef __KERNEL__ diff --git a/include/linux/namei.h b/include/linux/namei.h index 05b441d..1e1febf 100644 --- a/include/linux/namei.h +++ b/include/linux/namei.h @@ -43,12 +43,14 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT, LAST_BIND}; * - internal "there are more path components" flag * - locked when lookup done with dcache_lock held * - dentry cache is untrusted; force a real lookup + * - suppress terminal automount */ #define LOOKUP_FOLLOW 1 #define LOOKUP_DIRECTORY 2 #define LOOKUP_CONTINUE 4 #define LOOKUP_PARENT 16 #define LOOKUP_REVAL 64 +#define LOOKUP_NO_AUTOMOUNT 128 /* * Intent data */