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Subject[PATCH 11/23] fs: Add /proc/namespaces/ directory
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This is a new directory to show all namespaces, which can be
accessed from this /proc tasks credentials.

Every /proc is related to a pid_namespace, and the pid_namespace
is related to a user_namespace. The items, we show in this
/proc/namespaces/ directory, are the namespaces,
whose user_namespaces are the same as /proc's user_namespace,
or their descendants.

Say, /proc has pid_ns->user_ns, so in /proc/namespace we show
only a ns, which is in_userns(pid_ns->user_ns, ns->user_ns).

The final result is like below:

# ls /proc/namespaces/ -l
lrwxrwxrwx 1 root root 0 Jul 29 16:50 'cgroup:[4026531835]' -> 'cgroup:[4026531835]'
lrwxrwxrwx 1 root root 0 Jul 29 16:50 'ipc:[4026531839]' -> 'ipc:[4026531839]'
lrwxrwxrwx 1 root root 0 Jul 29 16:50 'mnt:[4026531840]' -> 'mnt:[4026531840]'
lrwxrwxrwx 1 root root 0 Jul 29 16:50 'mnt:[4026531861]' -> 'mnt:[4026531861]'
lrwxrwxrwx 1 root root 0 Jul 29 16:50 'mnt:[4026532133]' -> 'mnt:[4026532133]'
lrwxrwxrwx 1 root root 0 Jul 29 16:50 'mnt:[4026532134]' -> 'mnt:[4026532134]'
lrwxrwxrwx 1 root root 0 Jul 29 16:50 'mnt:[4026532135]' -> 'mnt:[4026532135]'
lrwxrwxrwx 1 root root 0 Jul 29 16:50 'mnt:[4026532136]' -> 'mnt:[4026532136]'
lrwxrwxrwx 1 root root 0 Jul 29 16:50 'net:[4026531993]' -> 'net:[4026531993]'
lrwxrwxrwx 1 root root 0 Jul 29 16:50 'pid:[4026531836]' -> 'pid:[4026531836]'
lrwxrwxrwx 1 root root 0 Jul 29 16:50 'time:[4026531834]' -> 'time:[4026531834]'
lrwxrwxrwx 1 root root 0 Jul 29 16:50 'user:[4026531837]' -> 'user:[4026531837]'
lrwxrwxrwx 1 root root 0 Jul 29 16:50 'uts:[4026531838]' -> 'uts:[4026531838]'

Every namespace may be open like ordinary file in /proc/[pid]/ns.

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
---
fs/nsfs.c | 2
fs/proc/Makefile | 1
fs/proc/internal.h | 16 ++
fs/proc/namespaces.c | 314 +++++++++++++++++++++++++++++++++++++++++++++++
fs/proc/root.c | 17 ++-
include/linux/proc_fs.h | 1
6 files changed, 345 insertions(+), 6 deletions(-)
create mode 100644 fs/proc/namespaces.c

diff --git a/fs/nsfs.c b/fs/nsfs.c
index ee4be67d3a0b..61b789d2089c 100644
--- a/fs/nsfs.c
+++ b/fs/nsfs.c
@@ -58,7 +58,7 @@ static void nsfs_evict(struct inode *inode)
ns->ops->put(ns);
}

-static int __ns_get_path(struct path *path, struct ns_common *ns)
+int __ns_get_path(struct path *path, struct ns_common *ns)
{
struct vfsmount *mnt = nsfs_mnt;
struct dentry *dentry;
diff --git a/fs/proc/Makefile b/fs/proc/Makefile
index dc2d51f42905..34ff671c6d59 100644
--- a/fs/proc/Makefile
+++ b/fs/proc/Makefile
@@ -25,6 +25,7 @@ proc-y += util.o
proc-y += version.o
proc-y += softirqs.o
proc-y += task_namespaces.o
+proc-y += namespaces.o
proc-y += self.o
proc-y += thread_self.o
proc-$(CONFIG_PROC_SYSCTL) += proc_sysctl.o
diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index 572757ff97be..d19fe5574799 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -134,10 +134,11 @@ void task_dump_owner(struct task_struct *task, umode_t mode,
kuid_t *ruid, kgid_t *rgid);

unsigned name_to_int(const struct qstr *qstr);
-/*
- * Offset of the first process in the /proc root directory..
- */
-#define FIRST_PROCESS_ENTRY 256
+
+/* Offset of "namespaces" entry in /proc root directory */
+#define NAMESPACES_ENTRY 256
+/* Offset of the first process in the /proc root directory */
+#define FIRST_PROCESS_ENTRY (NAMESPACES_ENTRY + 1)

/* Worst case buffer size needed for holding an integer. */
#define PROC_NUMBUF 13
@@ -168,6 +169,7 @@ extern void proc_pid_evict_inode(struct proc_inode *);
extern struct inode *proc_pid_make_inode(struct super_block *, struct task_struct *, umode_t);
extern void pid_update_inode(struct task_struct *, struct inode *);
extern int pid_delete_dentry(const struct dentry *);
+extern int proc_emit_namespaces(struct file *, struct dir_context *);
extern int proc_pid_readdir(struct file *, struct dir_context *);
struct dentry *proc_pid_lookup(struct dentry *, unsigned int);
extern loff_t mem_lseek(struct file *, loff_t, int);
@@ -222,6 +224,12 @@ void set_proc_pid_nlink(void);
extern struct inode *proc_get_inode(struct super_block *, struct proc_dir_entry *);
extern void proc_entry_rundown(struct proc_dir_entry *);

+/*
+ * namespaces.c
+ */
+extern int proc_setup_namespaces(struct super_block *);
+extern void proc_namespaces_init(void);
+
/*
* task_namespaces.c
*/
diff --git a/fs/proc/namespaces.c b/fs/proc/namespaces.c
new file mode 100644
index 000000000000..ab47e1555619
--- /dev/null
+++ b/fs/proc/namespaces.c
@@ -0,0 +1,314 @@
+#include <linux/pid_namespace.h>
+#include <linux/user_namespace.h>
+#include <linux/namei.h>
+#include "internal.h"
+
+static unsigned namespaces_inum __ro_after_init;
+
+int proc_emit_namespaces(struct file *file, struct dir_context *ctx)
+{
+ struct proc_fs_info *fs_info = proc_sb_info(file_inode(file)->i_sb);
+ struct inode *inode = d_inode(fs_info->proc_namespaces);
+
+ return dir_emit(ctx, "namespaces", 10, inode->i_ino, DT_DIR);
+}
+
+static int parse_namespace_dentry_name(const struct dentry *dentry,
+ const char **type, unsigned int *type_len, unsigned int *inum)
+{
+ const char *p, *name;
+ int count;
+
+ *type = name = dentry->d_name.name;
+ p = strchr(name, ':');
+ *type_len = p - name;
+ if (!p || p == name)
+ return -ENOENT;
+
+ p += 1;
+ if (sscanf(p, "[%u]%n", inum, &count) != 1 || *(p + count) != '\0' ||
+ *inum < PROC_NS_MIN_INO)
+ return -ENOENT;
+
+ return 0;
+}
+
+static struct ns_common *get_namespace_by_dentry(struct pid_namespace *pid_ns,
+ const struct dentry *dentry)
+{
+ unsigned int type_len, inum, p_inum;
+ struct user_namespace *user_ns;
+ struct ns_common *ns;
+ const char *type;
+
+ if (parse_namespace_dentry_name(dentry, &type, &type_len, &inum) < 0)
+ return NULL;
+
+ p_inum = inum - 1;
+ ns = ns_get_next(&p_inum);
+ if (!ns)
+ return NULL;
+
+ if (ns->inum != inum || strncmp(type, ns->ops->name, type_len) != 0 ||
+ ns->ops->name[type_len] != '\0') {
+ ns->ops->put(ns);
+ return NULL;
+ }
+
+ if (ns->ops != &userns_operations)
+ user_ns = ns->ops->owner(ns);
+ else
+ user_ns = container_of(ns, struct user_namespace, ns);
+
+ if (!in_userns(pid_ns->user_ns, user_ns)) {
+ ns->ops->put(ns);
+ return NULL;
+ }
+
+ return ns;
+}
+
+static struct dentry *proc_namespace_instantiate(struct dentry *dentry,
+ struct task_struct *task, const void *ptr);
+
+static struct dentry *proc_namespaces_lookup(struct inode *dir, struct dentry *dentry,
+ unsigned int flags)
+{
+ struct pid_namespace *pid_ns = proc_pid_ns(dir->i_sb);
+ struct task_struct *task;
+ struct ns_common *ns;
+
+ ns = get_namespace_by_dentry(pid_ns, dentry);
+ if (!ns)
+ return ERR_PTR(-ENOENT);
+
+ read_lock(&tasklist_lock);
+ task = get_task_struct(pid_ns->child_reaper);
+ read_unlock(&tasklist_lock);
+
+ dentry = proc_namespace_instantiate(dentry, task, ns);
+ put_task_struct(task);
+ ns->ops->put(ns);
+
+ return dentry;
+}
+
+static int proc_namespaces_permission(struct inode *inode, int mask)
+{
+ if ((mask & MAY_EXEC) && S_ISLNK(inode->i_mode))
+ return -EACCES;
+
+ return 0;
+}
+
+static int proc_namespaces_getattr(const struct path *path, struct kstat *stat,
+ u32 request_mask, unsigned int query_flags)
+{
+ struct inode *inode = d_inode(path->dentry);
+
+ generic_fillattr(inode, stat);
+ return 0;
+}
+
+static const struct inode_operations proc_namespaces_inode_operations = {
+ .lookup = proc_namespaces_lookup,
+ .permission = proc_namespaces_permission,
+ .getattr = proc_namespaces_getattr,
+};
+
+static int proc_namespaces_readlink(struct dentry *dentry, char __user *buffer, int buflen)
+{
+ struct inode *dir = dentry->d_parent->d_inode;
+ struct pid_namespace *pid_ns = proc_pid_ns(dir->i_sb);
+ struct ns_common *ns;
+
+ ns = get_namespace_by_dentry(pid_ns, dentry);
+ if (!ns)
+ return -ENOENT;
+ ns->ops->put(ns);
+
+ /* proc_namespaces_readdir() creates dentry names in namespace format */
+ return readlink_copy(buffer, buflen, dentry->d_iname);
+}
+
+int __ns_get_path(struct path *path, struct ns_common *ns);
+
+static const char *proc_namespaces_getlink(struct dentry *dentry,
+ struct inode *inode, struct delayed_call *done)
+{
+ struct pid_namespace *pid_ns = proc_pid_ns(inode->i_sb);
+ struct ns_common *ns;
+ struct path path;
+ int ret;
+
+ if (!dentry)
+ return ERR_PTR(-ECHILD);
+
+ while (1) {
+ ret = -ENOENT;
+ ns = get_namespace_by_dentry(pid_ns, dentry);
+ if (!ns)
+ goto out;
+
+ ret = __ns_get_path(&path, ns);
+ if (ret == -EAGAIN)
+ continue;
+ if (ret)
+ goto out;
+ break;
+ }
+
+ ret = nd_jump_link(&path);
+out:
+ return ERR_PTR(ret);
+}
+
+static const struct inode_operations proc_namespaces_link_inode_operations = {
+ .readlink = proc_namespaces_readlink,
+ .get_link = proc_namespaces_getlink,
+};
+
+static int namespace_delete_dentry(const struct dentry *dentry)
+{
+ struct inode *dir = dentry->d_parent->d_inode;
+ struct pid_namespace *pid_ns = proc_pid_ns(dir->i_sb);
+ struct ns_common *ns;
+
+ ns = get_namespace_by_dentry(pid_ns, dentry);
+ if (!ns)
+ return 1;
+
+ ns->ops->put(ns);
+ return 0;
+}
+
+const struct dentry_operations namespaces_dentry_operations = {
+ .d_delete = namespace_delete_dentry,
+};
+
+static void namespace_update_inode(struct inode *inode)
+{
+ struct user_namespace *user_ns = proc_pid_ns(inode->i_sb)->user_ns;
+
+ inode->i_uid = make_kuid(user_ns, 0);
+ if (!uid_valid(inode->i_uid))
+ inode->i_uid = GLOBAL_ROOT_UID;
+
+ inode->i_gid = make_kgid(user_ns, 0);
+ if (!gid_valid(inode->i_gid))
+ inode->i_gid = GLOBAL_ROOT_GID;
+}
+
+static struct dentry *proc_namespace_instantiate(struct dentry *dentry,
+ struct task_struct *task, const void *ptr)
+{
+ const struct ns_common *ns = ptr;
+ struct inode *inode;
+ struct proc_inode *ei;
+
+ /*
+ * Create inode with credentials of @task, and add it to @task's
+ * quick removal list.
+ */
+ inode = proc_pid_make_inode(dentry->d_sb, task, S_IFLNK | S_IRWXUGO);
+ if (!inode)
+ return ERR_PTR(-ENOENT);
+
+ ei = PROC_I(inode);
+ inode->i_op = &proc_namespaces_link_inode_operations;
+ ei->ns_ops = ns->ops;
+ namespace_update_inode(inode);
+
+ d_set_d_op(dentry, &namespaces_dentry_operations);
+ return d_splice_alias(inode, dentry);
+}
+
+static int proc_namespaces_readdir(struct file *file, struct dir_context *ctx)
+{
+ struct pid_namespace *pid_ns = proc_pid_ns(file_inode(file)->i_sb);
+ struct user_namespace *user_ns;
+ struct task_struct *task;
+ struct ns_common *ns;
+ unsigned int inum;
+
+ read_lock(&tasklist_lock);
+ task = get_task_struct(pid_ns->child_reaper);
+ read_unlock(&tasklist_lock);
+
+ if (!dir_emit_dots(file, ctx))
+ goto out;
+
+ inum = ctx->pos - 2;
+ while ((ns = ns_get_next(&inum)) != NULL) {
+ unsigned int len;
+ char name[32];
+
+ if (ns->ops != &userns_operations)
+ user_ns = ns->ops->owner(ns);
+ else
+ user_ns = container_of(ns, struct user_namespace, ns);
+
+ if (!in_userns(pid_ns->user_ns, user_ns))
+ goto next;
+
+ len = snprintf(name, sizeof(name), "%s:[%u]", ns->ops->name, inum);
+
+ if (!proc_fill_cache(file, ctx, name, len,
+ proc_namespace_instantiate, task, ns)) {
+ ns->ops->put(ns);
+ break;
+ }
+next:
+ ns->ops->put(ns);
+ ctx->pos = inum + 2;
+ }
+out:
+ put_task_struct(task);
+ return 0;
+}
+
+static const struct file_operations proc_namespaces_file_operations = {
+ .read = generic_read_dir,
+ .iterate_shared = proc_namespaces_readdir,
+ .llseek = generic_file_llseek,
+};
+
+int proc_setup_namespaces(struct super_block *s)
+{
+ struct proc_fs_info *fs_info = proc_sb_info(s);
+ struct inode *root_inode = d_inode(s->s_root);
+ struct dentry *namespaces;
+ int ret = -ENOMEM;
+
+ inode_lock(root_inode);
+ namespaces = d_alloc_name(s->s_root, "namespaces");
+ if (namespaces) {
+ struct inode *inode = new_inode_pseudo(s);
+ if (inode) {
+ inode->i_ino = namespaces_inum;
+ inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
+ inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO;
+ inode->i_uid = GLOBAL_ROOT_UID;
+ inode->i_gid = GLOBAL_ROOT_GID;
+ inode->i_op = &proc_namespaces_inode_operations;
+ inode->i_fop = &proc_namespaces_file_operations;
+ d_add(namespaces, inode);
+ ret = 0;
+ } else {
+ dput(namespaces);
+ }
+ }
+ inode_unlock(root_inode);
+
+ if (ret)
+ pr_err("proc_setup_namespaces: can't allocate /proc/namespaces\n");
+ else
+ fs_info->proc_namespaces = namespaces;
+
+ return ret;
+}
+
+void __init proc_namespaces_init(void)
+{
+ proc_alloc_inum(&namespaces_inum);
+}
diff --git a/fs/proc/root.c b/fs/proc/root.c
index 5e444d4f9717..e4e4f90fca3d 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -206,6 +206,10 @@ static int proc_fill_super(struct super_block *s, struct fs_context *fc)
return -ENOMEM;
}

+ ret = proc_setup_namespaces(s);
+ if (ret)
+ return ret;
+
ret = proc_setup_self(s);
if (ret) {
return ret;
@@ -272,6 +276,9 @@ static void proc_kill_sb(struct super_block *sb)
dput(fs_info->proc_self);
dput(fs_info->proc_thread_self);

+ if (fs_info->proc_namespaces)
+ dput(fs_info->proc_namespaces);
+
kill_anon_super(sb);
put_pid_ns(fs_info->pid_ns);
kfree(fs_info);
@@ -289,6 +296,7 @@ void __init proc_root_init(void)
{
proc_init_kmemcache();
set_proc_pid_nlink();
+ proc_namespaces_init();
proc_self_init();
proc_thread_self_init();
proc_symlink("mounts", NULL, "self/mounts");
@@ -326,8 +334,15 @@ static struct dentry *proc_root_lookup(struct inode * dir, struct dentry * dentr

static int proc_root_readdir(struct file *file, struct dir_context *ctx)
{
- if (ctx->pos < FIRST_PROCESS_ENTRY) {
+ if (ctx->pos < NAMESPACES_ENTRY) {
int error = proc_readdir(file, ctx);
+ if (unlikely(error <= 0))
+ return error;
+ ctx->pos = NAMESPACES_ENTRY;
+ }
+
+ if (ctx->pos == NAMESPACES_ENTRY) {
+ int error = proc_emit_namespaces(file, ctx);
if (unlikely(error <= 0))
return error;
ctx->pos = FIRST_PROCESS_ENTRY;
diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index 97b3f5f06db9..8b0002a6cacf 100644
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -61,6 +61,7 @@ struct proc_fs_info {
struct pid_namespace *pid_ns;
struct dentry *proc_self; /* For /proc/self */
struct dentry *proc_thread_self; /* For /proc/thread-self */
+ struct dentry *proc_namespaces; /* For /proc/namespaces */
kgid_t pid_gid;
enum proc_hidepid hide_pid;
enum proc_pidonly pidonly;

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