diff options
| -rw-r--r-- | fs/namespace.c | 37 | ||||
| -rw-r--r-- | fs/proc/root.c | 7 | ||||
| -rw-r--r-- | fs/sysfs/mount.c | 3 | ||||
| -rw-r--r-- | include/linux/fs.h | 1 | ||||
| -rw-r--r-- | include/linux/user_namespace.h | 4 | ||||
| -rw-r--r-- | kernel/user.c | 2 | ||||
| -rw-r--r-- | kernel/user_namespace.c | 2 |
7 files changed, 33 insertions, 23 deletions
diff --git a/fs/namespace.c b/fs/namespace.c index 64627f8..877e427 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -2867,25 +2867,38 @@ bool current_chrooted(void) return chrooted; } -void update_mnt_policy(struct user_namespace *userns) +bool fs_fully_visible(struct file_system_type *type) { struct mnt_namespace *ns = current->nsproxy->mnt_ns; struct mount *mnt; + bool visible = false; - down_read(&namespace_sem); + if (unlikely(!ns)) + return false; + + namespace_lock(); list_for_each_entry(mnt, &ns->list, mnt_list) { - switch (mnt->mnt.mnt_sb->s_magic) { - case SYSFS_MAGIC: - userns->may_mount_sysfs = true; - break; - case PROC_SUPER_MAGIC: - userns->may_mount_proc = true; - break; + struct mount *child; + if (mnt->mnt.mnt_sb->s_type != type) + continue; + + /* This mount is not fully visible if there are any child mounts + * that cover anything except for empty directories. + */ + list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) { + struct inode *inode = child->mnt_mountpoint->d_inode; + if (!S_ISDIR(inode->i_mode)) + goto next; + if (inode->i_nlink != 2) + goto next; } - if (userns->may_mount_sysfs && userns->may_mount_proc) - break; + visible = true; + goto found; + next: ; } - up_read(&namespace_sem); +found: + namespace_unlock(); + return visible; } static void *mntns_get(struct task_struct *task) diff --git a/fs/proc/root.c b/fs/proc/root.c index 38bd5d4..45e5fb7 100644 --- a/fs/proc/root.c +++ b/fs/proc/root.c @@ -110,8 +110,11 @@ static struct dentry *proc_mount(struct file_system_type *fs_type, ns = task_active_pid_ns(current); options = data; - if (!current_user_ns()->may_mount_proc || - !ns_capable(ns->user_ns, CAP_SYS_ADMIN)) + if (!capable(CAP_SYS_ADMIN) && !fs_fully_visible(fs_type)) + return ERR_PTR(-EPERM); + + /* Does the mounter have privilege over the pid namespace? */ + if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN)) return ERR_PTR(-EPERM); } diff --git a/fs/sysfs/mount.c b/fs/sysfs/mount.c index afd8327..4a2da3a 100644 --- a/fs/sysfs/mount.c +++ b/fs/sysfs/mount.c @@ -112,7 +112,8 @@ static struct dentry *sysfs_mount(struct file_system_type *fs_type, struct super_block *sb; int error; - if (!(flags & MS_KERNMOUNT) && !current_user_ns()->may_mount_sysfs) + if (!(flags & MS_KERNMOUNT) && !capable(CAP_SYS_ADMIN) && + !fs_fully_visible(fs_type)) return ERR_PTR(-EPERM); info = kzalloc(sizeof(*info), GFP_KERNEL); diff --git a/include/linux/fs.h b/include/linux/fs.h index 9818747..3050c62 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1897,6 +1897,7 @@ extern int vfs_ustat(dev_t, struct kstatfs *); extern int freeze_super(struct super_block *super); extern int thaw_super(struct super_block *super); extern bool our_mnt(struct vfsmount *mnt); +extern bool fs_fully_visible(struct file_system_type *); extern int current_umask(void); diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h index b6b215f..4ce0093 100644 --- a/include/linux/user_namespace.h +++ b/include/linux/user_namespace.h @@ -26,8 +26,6 @@ struct user_namespace { kuid_t owner; kgid_t group; unsigned int proc_inum; - bool may_mount_sysfs; - bool may_mount_proc; }; extern struct user_namespace init_user_ns; @@ -84,6 +82,4 @@ static inline void put_user_ns(struct user_namespace *ns) #endif -void update_mnt_policy(struct user_namespace *userns); - #endif /* _LINUX_USER_H */ diff --git a/kernel/user.c b/kernel/user.c index 69b4c3d..5bbb919 100644 --- a/kernel/user.c +++ b/kernel/user.c @@ -51,8 +51,6 @@ struct user_namespace init_user_ns = { .owner = GLOBAL_ROOT_UID, .group = GLOBAL_ROOT_GID, .proc_inum = PROC_USER_INIT_INO, - .may_mount_sysfs = true, - .may_mount_proc = true, }; EXPORT_SYMBOL_GPL(init_user_ns); diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c index d8c30db..d58ad1e 100644 --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -97,8 +97,6 @@ int create_user_ns(struct cred *new) set_cred_user_ns(new, ns); - update_mnt_policy(ns); - return 0; } |
