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-rw-r--r--fs/mount.h12
-rw-r--r--fs/namespace.c91
-rw-r--r--fs/proc_namespace.c4
-rw-r--r--include/linux/mount.h4
4 files changed, 90 insertions, 21 deletions
diff --git a/fs/mount.h b/fs/mount.h
index 711a4093e475..c7abb7b394d8 100644
--- a/fs/mount.h
+++ b/fs/mount.h
@@ -9,7 +9,13 @@ struct mnt_namespace {
atomic_t count;
struct ns_common ns;
struct mount * root;
+ /*
+ * Traversal and modification of .list is protected by either
+ * - taking namespace_sem for write, OR
+ * - taking namespace_sem for read AND taking .ns_lock.
+ */
struct list_head list;
+ spinlock_t ns_lock;
struct user_namespace *user_ns;
struct ucounts *ucounts;
u64 seq; /* Sequence number to prevent loops */
@@ -133,9 +139,7 @@ struct proc_mounts {
struct mnt_namespace *ns;
struct path root;
int (*show)(struct seq_file *, struct vfsmount *);
- void *cached_mount;
- u64 cached_event;
- loff_t cached_index;
+ struct mount cursor;
};
extern const struct seq_operations mounts_op;
@@ -153,3 +157,5 @@ static inline bool is_anon_ns(struct mnt_namespace *ns)
{
return ns->seq == 0;
}
+
+extern void mnt_cursor_del(struct mnt_namespace *ns, struct mount *cursor);
diff --git a/fs/namespace.c b/fs/namespace.c
index a28e4db075ed..3ee236f228a2 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -648,6 +648,21 @@ struct vfsmount *lookup_mnt(const struct path *path)
return m;
}
+static inline void lock_ns_list(struct mnt_namespace *ns)
+{
+ spin_lock(&ns->ns_lock);
+}
+
+static inline void unlock_ns_list(struct mnt_namespace *ns)
+{
+ spin_unlock(&ns->ns_lock);
+}
+
+static inline bool mnt_is_cursor(struct mount *mnt)
+{
+ return mnt->mnt.mnt_flags & MNT_CURSOR;
+}
+
/*
* __is_local_mountpoint - Test to see if dentry is a mountpoint in the
* current mount namespace.
@@ -673,11 +688,15 @@ bool __is_local_mountpoint(struct dentry *dentry)
goto out;
down_read(&namespace_sem);
+ lock_ns_list(ns);
list_for_each_entry(mnt, &ns->list, mnt_list) {
+ if (mnt_is_cursor(mnt))
+ continue;
is_covered = (mnt->mnt_mountpoint == dentry);
if (is_covered)
break;
}
+ unlock_ns_list(ns);
up_read(&namespace_sem);
out:
return is_covered;
@@ -1245,46 +1264,71 @@ struct vfsmount *mnt_clone_internal(const struct path *path)
}
#ifdef CONFIG_PROC_FS
+static struct mount *mnt_list_next(struct mnt_namespace *ns,
+ struct list_head *p)
+{
+ struct mount *mnt, *ret = NULL;
+
+ lock_ns_list(ns);
+ list_for_each_continue(p, &ns->list) {
+ mnt = list_entry(p, typeof(*mnt), mnt_list);
+ if (!mnt_is_cursor(mnt)) {
+ ret = mnt;
+ break;
+ }
+ }
+ unlock_ns_list(ns);
+
+ return ret;
+}
+
/* iterator; we want it to have access to namespace_sem, thus here... */
static void *m_start(struct seq_file *m, loff_t *pos)
{
struct proc_mounts *p = m->private;
+ struct list_head *prev;
down_read(&namespace_sem);
- if (p->cached_event == p->ns->event) {
- void *v = p->cached_mount;
- if (*pos == p->cached_index)
- return v;
- if (*pos == p->cached_index + 1) {
- v = seq_list_next(v, &p->ns->list, &p->cached_index);
- return p->cached_mount = v;
- }
+ if (!*pos) {
+ prev = &p->ns->list;
+ } else {
+ prev = &p->cursor.mnt_list;
+
+ /* Read after we'd reached the end? */
+ if (list_empty(prev))
+ return NULL;
}
- p->cached_event = p->ns->event;
- p->cached_mount = seq_list_start(&p->ns->list, *pos);
- p->cached_index = *pos;
- return p->cached_mount;
+ return mnt_list_next(p->ns, prev);
}
static void *m_next(struct seq_file *m, void *v, loff_t *pos)
{
struct proc_mounts *p = m->private;
+ struct mount *mnt = v;
- p->cached_mount = seq_list_next(v, &p->ns->list, pos);
- p->cached_index = *pos;
- return p->cached_mount;
+ ++*pos;
+ return mnt_list_next(p->ns, &mnt->mnt_list);
}
static void m_stop(struct seq_file *m, void *v)
{
+ struct proc_mounts *p = m->private;
+ struct mount *mnt = v;
+
+ lock_ns_list(p->ns);
+ if (mnt)
+ list_move_tail(&p->cursor.mnt_list, &mnt->mnt_list);
+ else
+ list_del_init(&p->cursor.mnt_list);
+ unlock_ns_list(p->ns);
up_read(&namespace_sem);
}
static int m_show(struct seq_file *m, void *v)
{
struct proc_mounts *p = m->private;
- struct mount *r = list_entry(v, struct mount, mnt_list);
+ struct mount *r = v;
return p->show(m, &r->mnt);
}
@@ -1294,6 +1338,15 @@ const struct seq_operations mounts_op = {
.stop = m_stop,
.show = m_show,
};
+
+void mnt_cursor_del(struct mnt_namespace *ns, struct mount *cursor)
+{
+ down_read(&namespace_sem);
+ lock_ns_list(ns);
+ list_del(&cursor->mnt_list);
+ unlock_ns_list(ns);
+ up_read(&namespace_sem);
+}
#endif /* CONFIG_PROC_FS */
/**
@@ -3202,6 +3255,7 @@ static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns, bool a
atomic_set(&new_ns->count, 1);
INIT_LIST_HEAD(&new_ns->list);
init_waitqueue_head(&new_ns->poll);
+ spin_lock_init(&new_ns->ns_lock);
new_ns->user_ns = get_user_ns(user_ns);
new_ns->ucounts = ucounts;
return new_ns;
@@ -3842,10 +3896,14 @@ static bool mnt_already_visible(struct mnt_namespace *ns,
bool visible = false;
down_read(&namespace_sem);
+ lock_ns_list(ns);
list_for_each_entry(mnt, &ns->list, mnt_list) {
struct mount *child;
int mnt_flags;
+ if (mnt_is_cursor(mnt))
+ continue;
+
if (mnt->mnt.mnt_sb->s_type != sb->s_type)
continue;
@@ -3893,6 +3951,7 @@ static bool mnt_already_visible(struct mnt_namespace *ns,
next: ;
}
found:
+ unlock_ns_list(ns);
up_read(&namespace_sem);
return visible;
}
diff --git a/fs/proc_namespace.c b/fs/proc_namespace.c
index 273ee82d8aa9..e4d70c0dffe9 100644
--- a/fs/proc_namespace.c
+++ b/fs/proc_namespace.c
@@ -279,7 +279,8 @@ static int mounts_open_common(struct inode *inode, struct file *file,
p->ns = ns;
p->root = root;
p->show = show;
- p->cached_event = ~0ULL;
+ INIT_LIST_HEAD(&p->cursor.mnt_list);
+ p->cursor.mnt.mnt_flags = MNT_CURSOR;
return 0;
@@ -296,6 +297,7 @@ static int mounts_release(struct inode *inode, struct file *file)
struct seq_file *m = file->private_data;
struct proc_mounts *p = m->private;
path_put(&p->root);
+ mnt_cursor_del(p->ns, &p->cursor);
put_mnt_ns(p->ns);
return seq_release_private(inode, file);
}
diff --git a/include/linux/mount.h b/include/linux/mount.h
index bf8cc4108b8f..7edac8c7a9c1 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -50,7 +50,8 @@ struct fs_context;
#define MNT_ATIME_MASK (MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME )
#define MNT_INTERNAL_FLAGS (MNT_SHARED | MNT_WRITE_HOLD | MNT_INTERNAL | \
- MNT_DOOMED | MNT_SYNC_UMOUNT | MNT_MARKED)
+ MNT_DOOMED | MNT_SYNC_UMOUNT | MNT_MARKED | \
+ MNT_CURSOR)
#define MNT_INTERNAL 0x4000
@@ -64,6 +65,7 @@ struct fs_context;
#define MNT_SYNC_UMOUNT 0x2000000
#define MNT_MARKED 0x4000000
#define MNT_UMOUNT 0x8000000
+#define MNT_CURSOR 0x10000000
struct vfsmount {
struct dentry *mnt_root; /* root of the mounted tree */
Copyright © 1996 – 2023 Jason A. Donenfeld. All Rights Reverse Engineered.