v4.19.13 snapshot.
diff --git a/fs/proc/namespaces.c b/fs/proc/namespaces.c
new file mode 100644
index 0000000..dd2b35f
--- /dev/null
+++ b/fs/proc/namespaces.c
@@ -0,0 +1,175 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/proc_fs.h>
+#include <linux/nsproxy.h>
+#include <linux/ptrace.h>
+#include <linux/namei.h>
+#include <linux/file.h>
+#include <linux/utsname.h>
+#include <net/net_namespace.h>
+#include <linux/ipc_namespace.h>
+#include <linux/pid_namespace.h>
+#include <linux/user_namespace.h>
+#include "internal.h"
+
+
+static const struct proc_ns_operations *ns_entries[] = {
+#ifdef CONFIG_NET_NS
+ &netns_operations,
+#endif
+#ifdef CONFIG_UTS_NS
+ &utsns_operations,
+#endif
+#ifdef CONFIG_IPC_NS
+ &ipcns_operations,
+#endif
+#ifdef CONFIG_PID_NS
+ &pidns_operations,
+ &pidns_for_children_operations,
+#endif
+#ifdef CONFIG_USER_NS
+ &userns_operations,
+#endif
+ &mntns_operations,
+#ifdef CONFIG_CGROUPS
+ &cgroupns_operations,
+#endif
+};
+
+static const char *proc_ns_get_link(struct dentry *dentry,
+ struct inode *inode,
+ struct delayed_call *done)
+{
+ const struct proc_ns_operations *ns_ops = PROC_I(inode)->ns_ops;
+ struct task_struct *task;
+ struct path ns_path;
+ void *error = ERR_PTR(-EACCES);
+
+ if (!dentry)
+ return ERR_PTR(-ECHILD);
+
+ task = get_proc_task(inode);
+ if (!task)
+ return error;
+
+ if (ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS)) {
+ error = ns_get_path(&ns_path, task, ns_ops);
+ if (!error)
+ nd_jump_link(&ns_path);
+ }
+ put_task_struct(task);
+ return error;
+}
+
+static int proc_ns_readlink(struct dentry *dentry, char __user *buffer, int buflen)
+{
+ struct inode *inode = d_inode(dentry);
+ const struct proc_ns_operations *ns_ops = PROC_I(inode)->ns_ops;
+ struct task_struct *task;
+ char name[50];
+ int res = -EACCES;
+
+ task = get_proc_task(inode);
+ if (!task)
+ return res;
+
+ if (ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS)) {
+ res = ns_get_name(name, sizeof(name), task, ns_ops);
+ if (res >= 0)
+ res = readlink_copy(buffer, buflen, name);
+ }
+ put_task_struct(task);
+ return res;
+}
+
+static const struct inode_operations proc_ns_link_inode_operations = {
+ .readlink = proc_ns_readlink,
+ .get_link = proc_ns_get_link,
+ .setattr = proc_setattr,
+};
+
+static struct dentry *proc_ns_instantiate(struct dentry *dentry,
+ struct task_struct *task, const void *ptr)
+{
+ const struct proc_ns_operations *ns_ops = ptr;
+ struct inode *inode;
+ struct proc_inode *ei;
+
+ 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_ns_link_inode_operations;
+ ei->ns_ops = ns_ops;
+ pid_update_inode(task, inode);
+
+ d_set_d_op(dentry, &pid_dentry_operations);
+ return d_splice_alias(inode, dentry);
+}
+
+static int proc_ns_dir_readdir(struct file *file, struct dir_context *ctx)
+{
+ struct task_struct *task = get_proc_task(file_inode(file));
+ const struct proc_ns_operations **entry, **last;
+
+ if (!task)
+ return -ENOENT;
+
+ if (!dir_emit_dots(file, ctx))
+ goto out;
+ if (ctx->pos >= 2 + ARRAY_SIZE(ns_entries))
+ goto out;
+ entry = ns_entries + (ctx->pos - 2);
+ last = &ns_entries[ARRAY_SIZE(ns_entries) - 1];
+ while (entry <= last) {
+ const struct proc_ns_operations *ops = *entry;
+ if (!proc_fill_cache(file, ctx, ops->name, strlen(ops->name),
+ proc_ns_instantiate, task, ops))
+ break;
+ ctx->pos++;
+ entry++;
+ }
+out:
+ put_task_struct(task);
+ return 0;
+}
+
+const struct file_operations proc_ns_dir_operations = {
+ .read = generic_read_dir,
+ .iterate_shared = proc_ns_dir_readdir,
+ .llseek = generic_file_llseek,
+};
+
+static struct dentry *proc_ns_dir_lookup(struct inode *dir,
+ struct dentry *dentry, unsigned int flags)
+{
+ struct task_struct *task = get_proc_task(dir);
+ const struct proc_ns_operations **entry, **last;
+ unsigned int len = dentry->d_name.len;
+ struct dentry *res = ERR_PTR(-ENOENT);
+
+ if (!task)
+ goto out_no_task;
+
+ last = &ns_entries[ARRAY_SIZE(ns_entries)];
+ for (entry = ns_entries; entry < last; entry++) {
+ if (strlen((*entry)->name) != len)
+ continue;
+ if (!memcmp(dentry->d_name.name, (*entry)->name, len))
+ break;
+ }
+ if (entry == last)
+ goto out;
+
+ res = proc_ns_instantiate(dentry, task, *entry);
+out:
+ put_task_struct(task);
+out_no_task:
+ return res;
+}
+
+const struct inode_operations proc_ns_dir_inode_operations = {
+ .lookup = proc_ns_dir_lookup,
+ .getattr = pid_getattr,
+ .setattr = proc_setattr,
+};