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![Eric W. Biederman](/assets/img/avatar_default.png)
Assign a unique proc inode to each namespace, and use that inode number to ensure we only allocate at most one proc inode for every namespace in proc. A single proc inode per namespace allows userspace to test to see if two processes are in the same namespace. This has been a long requested feature and only blocked because a naive implementation would put the id in a global space and would ultimately require having a namespace for the names of namespaces, making migration and certain virtualization tricks impossible. We still don't have per superblock inode numbers for proc, which appears necessary for application unaware checkpoint/restart and migrations (if the application is using namespace file descriptors) but that is now allowd by the design if it becomes important. I have preallocated the ipc and uts initial proc inode numbers so their structures can be statically initialized. Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
343 lines
7.2 KiB
C
343 lines
7.2 KiB
C
#include <linux/proc_fs.h>
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#include <linux/nsproxy.h>
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#include <linux/sched.h>
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#include <linux/ptrace.h>
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#include <linux/fs_struct.h>
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#include <linux/mount.h>
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#include <linux/path.h>
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#include <linux/namei.h>
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#include <linux/file.h>
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#include <linux/utsname.h>
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#include <net/net_namespace.h>
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#include <linux/ipc_namespace.h>
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#include <linux/pid_namespace.h>
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#include <linux/user_namespace.h>
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#include "internal.h"
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static const struct proc_ns_operations *ns_entries[] = {
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#ifdef CONFIG_NET_NS
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&netns_operations,
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#endif
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#ifdef CONFIG_UTS_NS
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&utsns_operations,
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#endif
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#ifdef CONFIG_IPC_NS
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&ipcns_operations,
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#endif
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#ifdef CONFIG_PID_NS
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&pidns_operations,
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#endif
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#ifdef CONFIG_USER_NS
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&userns_operations,
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#endif
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&mntns_operations,
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};
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static const struct file_operations ns_file_operations = {
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.llseek = no_llseek,
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};
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static const struct inode_operations ns_inode_operations = {
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.setattr = proc_setattr,
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};
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static int ns_delete_dentry(const struct dentry *dentry)
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{
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/* Don't cache namespace inodes when not in use */
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return 1;
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}
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static char *ns_dname(struct dentry *dentry, char *buffer, int buflen)
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{
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struct inode *inode = dentry->d_inode;
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const struct proc_ns_operations *ns_ops = PROC_I(inode)->ns_ops;
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return dynamic_dname(dentry, buffer, buflen, "%s:[%lu]",
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ns_ops->name, inode->i_ino);
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}
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const struct dentry_operations ns_dentry_operations =
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{
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.d_delete = ns_delete_dentry,
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.d_dname = ns_dname,
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};
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static struct dentry *proc_ns_get_dentry(struct super_block *sb,
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struct task_struct *task, const struct proc_ns_operations *ns_ops)
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{
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struct dentry *dentry, *result;
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struct inode *inode;
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struct proc_inode *ei;
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struct qstr qname = { .name = "", };
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void *ns;
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ns = ns_ops->get(task);
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if (!ns)
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return ERR_PTR(-ENOENT);
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dentry = d_alloc_pseudo(sb, &qname);
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if (!dentry) {
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ns_ops->put(ns);
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return ERR_PTR(-ENOMEM);
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}
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inode = iget_locked(sb, ns_ops->inum(ns));
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if (!inode) {
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dput(dentry);
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ns_ops->put(ns);
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return ERR_PTR(-ENOMEM);
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}
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ei = PROC_I(inode);
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if (inode->i_state & I_NEW) {
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inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
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inode->i_op = &ns_inode_operations;
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inode->i_mode = S_IFREG | S_IRUGO;
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inode->i_fop = &ns_file_operations;
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ei->ns_ops = ns_ops;
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ei->ns = ns;
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unlock_new_inode(inode);
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} else {
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ns_ops->put(ns);
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}
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d_set_d_op(dentry, &ns_dentry_operations);
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result = d_instantiate_unique(dentry, inode);
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if (result) {
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dput(dentry);
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dentry = result;
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}
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return dentry;
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}
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static void *proc_ns_follow_link(struct dentry *dentry, struct nameidata *nd)
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{
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struct inode *inode = dentry->d_inode;
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struct super_block *sb = inode->i_sb;
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struct proc_inode *ei = PROC_I(inode);
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struct task_struct *task;
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struct dentry *ns_dentry;
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void *error = ERR_PTR(-EACCES);
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task = get_proc_task(inode);
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if (!task)
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goto out;
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if (!ptrace_may_access(task, PTRACE_MODE_READ))
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goto out_put_task;
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ns_dentry = proc_ns_get_dentry(sb, task, ei->ns_ops);
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if (IS_ERR(ns_dentry)) {
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error = ERR_CAST(ns_dentry);
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goto out_put_task;
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}
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dput(nd->path.dentry);
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nd->path.dentry = ns_dentry;
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error = NULL;
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out_put_task:
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put_task_struct(task);
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out:
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return error;
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}
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static int proc_ns_readlink(struct dentry *dentry, char __user *buffer, int buflen)
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{
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struct inode *inode = dentry->d_inode;
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struct proc_inode *ei = PROC_I(inode);
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const struct proc_ns_operations *ns_ops = ei->ns_ops;
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struct task_struct *task;
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void *ns;
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char name[50];
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int len = -EACCES;
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task = get_proc_task(inode);
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if (!task)
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goto out;
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if (!ptrace_may_access(task, PTRACE_MODE_READ))
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goto out_put_task;
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len = -ENOENT;
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ns = ns_ops->get(task);
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if (!ns)
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goto out_put_task;
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snprintf(name, sizeof(name), "%s:[%u]", ns_ops->name, ns_ops->inum(ns));
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len = strlen(name);
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if (len > buflen)
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len = buflen;
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if (copy_to_user(buffer, name, len))
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len = -EFAULT;
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ns_ops->put(ns);
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out_put_task:
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put_task_struct(task);
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out:
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return len;
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}
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static const struct inode_operations proc_ns_link_inode_operations = {
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.readlink = proc_ns_readlink,
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.follow_link = proc_ns_follow_link,
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.setattr = proc_setattr,
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};
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static struct dentry *proc_ns_instantiate(struct inode *dir,
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struct dentry *dentry, struct task_struct *task, const void *ptr)
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{
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const struct proc_ns_operations *ns_ops = ptr;
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struct inode *inode;
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struct proc_inode *ei;
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struct dentry *error = ERR_PTR(-ENOENT);
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inode = proc_pid_make_inode(dir->i_sb, task);
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if (!inode)
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goto out;
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ei = PROC_I(inode);
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inode->i_mode = S_IFLNK|S_IRWXUGO;
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inode->i_op = &proc_ns_link_inode_operations;
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ei->ns_ops = ns_ops;
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d_set_d_op(dentry, &pid_dentry_operations);
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d_add(dentry, inode);
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/* Close the race of the process dying before we return the dentry */
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if (pid_revalidate(dentry, 0))
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error = NULL;
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out:
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return error;
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}
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static int proc_ns_fill_cache(struct file *filp, void *dirent,
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filldir_t filldir, struct task_struct *task,
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const struct proc_ns_operations *ops)
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{
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return proc_fill_cache(filp, dirent, filldir,
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ops->name, strlen(ops->name),
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proc_ns_instantiate, task, ops);
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}
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static int proc_ns_dir_readdir(struct file *filp, void *dirent,
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filldir_t filldir)
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{
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int i;
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struct dentry *dentry = filp->f_path.dentry;
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struct inode *inode = dentry->d_inode;
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struct task_struct *task = get_proc_task(inode);
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const struct proc_ns_operations **entry, **last;
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ino_t ino;
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int ret;
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ret = -ENOENT;
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if (!task)
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goto out_no_task;
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ret = 0;
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i = filp->f_pos;
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switch (i) {
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case 0:
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ino = inode->i_ino;
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if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0)
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goto out;
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i++;
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filp->f_pos++;
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/* fall through */
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case 1:
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ino = parent_ino(dentry);
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if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0)
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goto out;
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i++;
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filp->f_pos++;
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/* fall through */
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default:
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i -= 2;
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if (i >= ARRAY_SIZE(ns_entries)) {
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ret = 1;
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goto out;
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}
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entry = ns_entries + i;
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last = &ns_entries[ARRAY_SIZE(ns_entries) - 1];
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while (entry <= last) {
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if (proc_ns_fill_cache(filp, dirent, filldir,
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task, *entry) < 0)
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goto out;
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filp->f_pos++;
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entry++;
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}
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}
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ret = 1;
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out:
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put_task_struct(task);
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out_no_task:
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return ret;
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}
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const struct file_operations proc_ns_dir_operations = {
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.read = generic_read_dir,
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.readdir = proc_ns_dir_readdir,
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};
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static struct dentry *proc_ns_dir_lookup(struct inode *dir,
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struct dentry *dentry, unsigned int flags)
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{
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struct dentry *error;
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struct task_struct *task = get_proc_task(dir);
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const struct proc_ns_operations **entry, **last;
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unsigned int len = dentry->d_name.len;
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error = ERR_PTR(-ENOENT);
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if (!task)
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goto out_no_task;
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last = &ns_entries[ARRAY_SIZE(ns_entries)];
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for (entry = ns_entries; entry < last; entry++) {
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if (strlen((*entry)->name) != len)
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continue;
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if (!memcmp(dentry->d_name.name, (*entry)->name, len))
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break;
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}
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if (entry == last)
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goto out;
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error = proc_ns_instantiate(dir, dentry, task, *entry);
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out:
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put_task_struct(task);
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out_no_task:
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return error;
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}
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const struct inode_operations proc_ns_dir_inode_operations = {
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.lookup = proc_ns_dir_lookup,
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.getattr = pid_getattr,
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.setattr = proc_setattr,
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};
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struct file *proc_ns_fget(int fd)
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{
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struct file *file;
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file = fget(fd);
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if (!file)
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return ERR_PTR(-EBADF);
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if (file->f_op != &ns_file_operations)
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goto out_invalid;
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return file;
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out_invalid:
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fput(file);
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return ERR_PTR(-EINVAL);
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}
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bool proc_ns_inode(struct inode *inode)
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{
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return inode->i_fop == &ns_file_operations;
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}
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