![Kirill Tkhai](/assets/img/avatar_default.png)
Switch over mount namespaces to use the newly introduced common lifetime counter. Currently every namespace type has its own lifetime counter which is stored in the specific namespace struct. The lifetime counters are used identically for all namespaces types. Namespaces may of course have additional unrelated counters and these are not altered. This introduces a common lifetime counter into struct ns_common. The ns_common struct encompasses information that all namespaces share. That should include the lifetime counter since its common for all of them. It also allows us to unify the type of the counters across all namespaces. Most of them use refcount_t but one uses atomic_t and at least one uses kref. Especially the last one doesn't make much sense since it's just a wrapper around refcount_t since 2016 and actually complicates cleanup operations by having to use container_of() to cast the correct namespace struct out of struct ns_common. Having the lifetime counter for the namespaces in one place reduces maintenance cost. Not just because after switching all namespaces over we will have removed more code than we added but also because the logic is more easily understandable and we indicate to the user that the basic lifetime requirements for all namespaces are currently identical. Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com> Reviewed-by: Kees Cook <keescook@chromium.org> Acked-by: Christian Brauner <christian.brauner@ubuntu.com> Link: https://lore.kernel.org/r/159644980287.604812.761686947449081169.stgit@localhost.localdomain Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
161 lines
4.2 KiB
C
161 lines
4.2 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#include <linux/mount.h>
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#include <linux/seq_file.h>
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#include <linux/poll.h>
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#include <linux/ns_common.h>
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#include <linux/fs_pin.h>
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struct mnt_namespace {
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struct ns_common ns;
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struct mount * root;
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/*
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* Traversal and modification of .list is protected by either
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* - taking namespace_sem for write, OR
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* - taking namespace_sem for read AND taking .ns_lock.
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*/
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struct list_head list;
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spinlock_t ns_lock;
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struct user_namespace *user_ns;
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struct ucounts *ucounts;
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u64 seq; /* Sequence number to prevent loops */
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wait_queue_head_t poll;
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u64 event;
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unsigned int mounts; /* # of mounts in the namespace */
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unsigned int pending_mounts;
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} __randomize_layout;
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struct mnt_pcp {
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int mnt_count;
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int mnt_writers;
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};
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struct mountpoint {
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struct hlist_node m_hash;
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struct dentry *m_dentry;
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struct hlist_head m_list;
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int m_count;
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};
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struct mount {
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struct hlist_node mnt_hash;
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struct mount *mnt_parent;
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struct dentry *mnt_mountpoint;
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struct vfsmount mnt;
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union {
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struct rcu_head mnt_rcu;
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struct llist_node mnt_llist;
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};
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#ifdef CONFIG_SMP
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struct mnt_pcp __percpu *mnt_pcp;
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#else
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int mnt_count;
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int mnt_writers;
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#endif
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struct list_head mnt_mounts; /* list of children, anchored here */
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struct list_head mnt_child; /* and going through their mnt_child */
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struct list_head mnt_instance; /* mount instance on sb->s_mounts */
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const char *mnt_devname; /* Name of device e.g. /dev/dsk/hda1 */
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struct list_head mnt_list;
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struct list_head mnt_expire; /* link in fs-specific expiry list */
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struct list_head mnt_share; /* circular list of shared mounts */
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struct list_head mnt_slave_list;/* list of slave mounts */
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struct list_head mnt_slave; /* slave list entry */
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struct mount *mnt_master; /* slave is on master->mnt_slave_list */
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struct mnt_namespace *mnt_ns; /* containing namespace */
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struct mountpoint *mnt_mp; /* where is it mounted */
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union {
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struct hlist_node mnt_mp_list; /* list mounts with the same mountpoint */
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struct hlist_node mnt_umount;
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};
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struct list_head mnt_umounting; /* list entry for umount propagation */
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#ifdef CONFIG_FSNOTIFY
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struct fsnotify_mark_connector __rcu *mnt_fsnotify_marks;
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__u32 mnt_fsnotify_mask;
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#endif
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int mnt_id; /* mount identifier */
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int mnt_group_id; /* peer group identifier */
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int mnt_expiry_mark; /* true if marked for expiry */
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struct hlist_head mnt_pins;
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struct hlist_head mnt_stuck_children;
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} __randomize_layout;
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#define MNT_NS_INTERNAL ERR_PTR(-EINVAL) /* distinct from any mnt_namespace */
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static inline struct mount *real_mount(struct vfsmount *mnt)
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{
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return container_of(mnt, struct mount, mnt);
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}
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static inline int mnt_has_parent(struct mount *mnt)
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{
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return mnt != mnt->mnt_parent;
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}
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static inline int is_mounted(struct vfsmount *mnt)
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{
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/* neither detached nor internal? */
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return !IS_ERR_OR_NULL(real_mount(mnt)->mnt_ns);
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}
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extern struct mount *__lookup_mnt(struct vfsmount *, struct dentry *);
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extern int __legitimize_mnt(struct vfsmount *, unsigned);
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extern bool legitimize_mnt(struct vfsmount *, unsigned);
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static inline bool __path_is_mountpoint(const struct path *path)
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{
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struct mount *m = __lookup_mnt(path->mnt, path->dentry);
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return m && likely(!(m->mnt.mnt_flags & MNT_SYNC_UMOUNT));
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}
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extern void __detach_mounts(struct dentry *dentry);
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static inline void detach_mounts(struct dentry *dentry)
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{
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if (!d_mountpoint(dentry))
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return;
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__detach_mounts(dentry);
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}
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static inline void get_mnt_ns(struct mnt_namespace *ns)
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{
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refcount_inc(&ns->ns.count);
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}
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extern seqlock_t mount_lock;
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static inline void lock_mount_hash(void)
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{
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write_seqlock(&mount_lock);
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}
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static inline void unlock_mount_hash(void)
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{
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write_sequnlock(&mount_lock);
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}
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struct proc_mounts {
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struct mnt_namespace *ns;
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struct path root;
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int (*show)(struct seq_file *, struct vfsmount *);
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struct mount cursor;
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};
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extern const struct seq_operations mounts_op;
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extern bool __is_local_mountpoint(struct dentry *dentry);
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static inline bool is_local_mountpoint(struct dentry *dentry)
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{
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if (!d_mountpoint(dentry))
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return false;
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return __is_local_mountpoint(dentry);
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}
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static inline bool is_anon_ns(struct mnt_namespace *ns)
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{
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return ns->seq == 0;
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}
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extern void mnt_cursor_del(struct mnt_namespace *ns, struct mount *cursor);
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