[PATCH 6/6] Add an AT_NO_AUTOMOUNT flag to suppress terminal automount [ver #2]
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From: David Howells on 23 Jul 2010 11:20 This is an update required because the first patch in the series was also altered in the same area. David --- From: David Howells <dhowells(a)redhat.com> Subject: [PATCH] Add an AT_NO_AUTOMOUNT flag to suppress terminal automount Add an AT_NO_AUTOMOUNT flag to suppress terminal automounting of directories with follow_link semantics. This can be used by fstatat() 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 <dhowells(a)redhat.com> --- fs/namei.c | 6 ++++++ fs/stat.c | 4 +++- include/linux/fcntl.h | 1 + include/linux/namei.h | 2 ++ 4 files changed, 12 insertions(+), 1 deletions(-) diff --git a/fs/namei.c b/fs/namei.c index f2910b7..c154112 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -629,6 +629,12 @@ static int follow_automount(struct path *path, unsigned flags, int res) if (!path->dentry->d_op || !path->dentry->d_op->d_automount) return -EREMOTE; + /* We don't want to mount if someone supplied AT_NO_AUTOMOUNT + * and this is the terminal part of the path. + */ + if ((flags & LOOKUP_NO_AUTOMOUNT) && !(flags & LOOKUP_CONTINUE)) + return -EXDEV; /* we actually want to stop here */ + /* We want to mount if someone is trying to open/create a file of any * type under the mountpoint, wants to traverse through the mountpoint * or wants to open the mounted directory. diff --git a/fs/stat.c b/fs/stat.c index c4ecd52..bae6fa2 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 */ -- 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/ |