From: Miklos Szeredi Add a new mount flag "nosubmnt", which denies submounts for the owner. This would be useful, if we want to support traditional /etc/fstab based user mounts. In this case mount(8) would still have to be suid-root, to check the mountpoint against the user/users flag in /etc/fstab, but /etc/mtab would no longer be mandatory for storing the actual owner of the mount. Signed-off-by: Miklos Szeredi Acked-by: Serge Hallyn --- Index: linux/fs/namespace.c =================================================================== --- linux.orig/fs/namespace.c 2008-02-04 23:48:08.000000000 +0100 +++ linux/fs/namespace.c 2008-02-04 23:48:10.000000000 +0100 @@ -783,6 +783,7 @@ static void show_mnt_opts(struct seq_fil { MNT_NOATIME, ",noatime" }, { MNT_NODIRATIME, ",nodiratime" }, { MNT_RELATIME, ",relatime" }, + { MNT_NOSUBMNT, ",nosubmnt" }, { 0, NULL } }; const struct proc_fs_info *fs_infop; @@ -1189,6 +1190,9 @@ static bool permit_mount(struct nameidat if (S_ISLNK(inode->i_mode)) return false; + if (nd->path.mnt->mnt_flags & MNT_NOSUBMNT) + return false; + if (!is_mount_owner(nd->path.mnt, current->fsuid)) return false; @@ -2033,9 +2037,11 @@ long do_mount(char *dev_name, char *dir_ mnt_flags |= MNT_RELATIME; if (flags & MS_RDONLY) mnt_flags |= MNT_READONLY; + if (flags & MS_NOSUBMNT) + mnt_flags |= MNT_NOSUBMNT; - flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | - MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT); + flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_NOATIME | + MS_NODIRATIME | MS_RELATIME | MS_KERNMOUNT | MS_NOSUBMNT); /* ... and get the mountpoint */ retval = path_lookup(dir_name, LOOKUP_FOLLOW, &nd); Index: linux/include/linux/fs.h =================================================================== --- linux.orig/include/linux/fs.h 2008-02-04 23:48:08.000000000 +0100 +++ linux/include/linux/fs.h 2008-02-04 23:48:10.000000000 +0100 @@ -129,6 +129,7 @@ extern int dir_notify_enable; #define MS_KERNMOUNT (1<<22) /* this is a kern_mount call */ #define MS_I_VERSION (1<<23) /* Update inode I_version field */ #define MS_SETUSER (1<<24) /* set mnt_uid to current user */ +#define MS_NOSUBMNT (1<<25) /* don't allow unprivileged submounts */ #define MS_ACTIVE (1<<30) #define MS_NOUSER (1<<31) Index: linux/include/linux/mount.h =================================================================== --- linux.orig/include/linux/mount.h 2008-02-04 23:47:50.000000000 +0100 +++ linux/include/linux/mount.h 2008-02-04 23:48:10.000000000 +0100 @@ -30,6 +30,7 @@ struct mnt_namespace; #define MNT_NODIRATIME 0x10 #define MNT_RELATIME 0x20 #define MNT_READONLY 0x40 /* does the user want this to be r/o? */ +#define MNT_NOSUBMNT 0x80 #define MNT_SHRINKABLE 0x100 #define MNT_IMBALANCED_WRITE_COUNT 0x200 /* just for debugging */ -- -- 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/