[RFC][PATCH] xstat: Add an AT_NO_AUTOMOUNT flag to suppress terminal automount
in [Kernel]
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From: David Howells on 13 Jul 2010 18:50 [Based on the patch to add an automount dentry op] 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. Not-yet-signed-off-by: David Howells <dhowells(a)redhat.com> --- 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 19b99f9..a4deb2d 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -648,7 +648,8 @@ 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; @@ -668,8 +669,12 @@ 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; @@ -763,7 +768,7 @@ 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; @@ -1756,7 +1761,7 @@ 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 89d72fc..d9d6fca 100644 --- a/fs/stat.c +++ b/fs/stat.c @@ -180,11 +180,13 @@ int vfs_xstat(int dfd, const char __user *filename, int flags, struct path path; int error, lookup_flags; - if (flags & ~(AT_SYMLINK_NOFOLLOW | KSTAT_QUERY_FLAGS)) + if (flags & ~(AT_SYMLINK_NOFOLLOW | AT_NO_AUTOMOUNT | + KSTAT_QUERY_FLAGS)) return -EINVAL; stat->query_flags = flags & KSTAT_QUERY_FLAGS; lookup_flags = (flags & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW; + lookup_flags |= (flags & AT_NO_AUTOMOUNT) ? LOOKUP_NO_AUTOMOUNT : 0; error = user_path_at(dfd, filename, lookup_flags, &path); if (!error) { diff --git a/include/linux/fcntl.h b/include/linux/fcntl.h index bcf8083..768b0fd 100644 --- a/include/linux/fcntl.h +++ b/include/linux/fcntl.h @@ -46,6 +46,7 @@ unlinking file. */ #define AT_SYMLINK_FOLLOW 0x400 /* Follow symbolic links. */ #define AT_FORCE_ATTR_SYNC 0x800 /* Force the attributes to be sync'd with the server */ +#define AT_NO_AUTOMOUNT 0x1000 /* 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 */ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |