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https://github.com/torvalds/linux
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5e31d76f28
Before unlinking the inode, reset the current permissions of possible references like hardlinks, so granted permissions can not be retained across the device lifetime by creating hardlinks, in the unusual case that there is a user-writable directory on the same filesystem. Signed-off-by: Kay Sievers <kay.sievers@vrfy.org> Cc: stable <stable@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
391 lines
8.1 KiB
C
391 lines
8.1 KiB
C
/*
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* devtmpfs - kernel-maintained tmpfs-based /dev
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*
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* Copyright (C) 2009, Kay Sievers <kay.sievers@vrfy.org>
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*
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* During bootup, before any driver core device is registered,
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* devtmpfs, a tmpfs-based filesystem is created. Every driver-core
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* device which requests a device node, will add a node in this
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* filesystem.
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* By default, all devices are named after the the name of the
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* device, owned by root and have a default mode of 0600. Subsystems
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* can overwrite the default setting if needed.
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*/
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#include <linux/kernel.h>
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#include <linux/syscalls.h>
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#include <linux/mount.h>
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#include <linux/device.h>
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#include <linux/genhd.h>
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#include <linux/namei.h>
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#include <linux/fs.h>
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#include <linux/shmem_fs.h>
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#include <linux/cred.h>
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#include <linux/sched.h>
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#include <linux/init_task.h>
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static struct vfsmount *dev_mnt;
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#if defined CONFIG_DEVTMPFS_MOUNT
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static int dev_mount = 1;
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#else
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static int dev_mount;
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#endif
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static DEFINE_MUTEX(dirlock);
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static int __init mount_param(char *str)
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{
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dev_mount = simple_strtoul(str, NULL, 0);
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return 1;
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}
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__setup("devtmpfs.mount=", mount_param);
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static int dev_get_sb(struct file_system_type *fs_type, int flags,
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const char *dev_name, void *data, struct vfsmount *mnt)
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{
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return get_sb_single(fs_type, flags, data, shmem_fill_super, mnt);
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}
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static struct file_system_type dev_fs_type = {
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.name = "devtmpfs",
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.get_sb = dev_get_sb,
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.kill_sb = kill_litter_super,
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};
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#ifdef CONFIG_BLOCK
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static inline int is_blockdev(struct device *dev)
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{
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return dev->class == &block_class;
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}
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#else
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static inline int is_blockdev(struct device *dev) { return 0; }
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#endif
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static int dev_mkdir(const char *name, mode_t mode)
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{
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struct nameidata nd;
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struct dentry *dentry;
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int err;
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err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,
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name, LOOKUP_PARENT, &nd);
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if (err)
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return err;
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dentry = lookup_create(&nd, 1);
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if (!IS_ERR(dentry)) {
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err = vfs_mkdir(nd.path.dentry->d_inode, dentry, mode);
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if (!err)
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/* mark as kernel-created inode */
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dentry->d_inode->i_private = &dev_mnt;
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dput(dentry);
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} else {
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err = PTR_ERR(dentry);
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}
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mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
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path_put(&nd.path);
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return err;
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}
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static int create_path(const char *nodepath)
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{
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int err;
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mutex_lock(&dirlock);
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err = dev_mkdir(nodepath, 0755);
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if (err == -ENOENT) {
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char *path;
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char *s;
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/* parent directories do not exist, create them */
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path = kstrdup(nodepath, GFP_KERNEL);
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if (!path) {
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err = -ENOMEM;
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goto out;
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}
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s = path;
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for (;;) {
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s = strchr(s, '/');
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if (!s)
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break;
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s[0] = '\0';
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err = dev_mkdir(path, 0755);
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if (err && err != -EEXIST)
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break;
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s[0] = '/';
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s++;
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}
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kfree(path);
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}
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out:
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mutex_unlock(&dirlock);
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return err;
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}
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int devtmpfs_create_node(struct device *dev)
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{
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const char *tmp = NULL;
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const char *nodename;
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const struct cred *curr_cred;
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mode_t mode = 0;
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struct nameidata nd;
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struct dentry *dentry;
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int err;
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if (!dev_mnt)
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return 0;
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nodename = device_get_devnode(dev, &mode, &tmp);
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if (!nodename)
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return -ENOMEM;
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if (mode == 0)
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mode = 0600;
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if (is_blockdev(dev))
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mode |= S_IFBLK;
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else
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mode |= S_IFCHR;
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curr_cred = override_creds(&init_cred);
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err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,
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nodename, LOOKUP_PARENT, &nd);
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if (err == -ENOENT) {
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create_path(nodename);
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err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,
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nodename, LOOKUP_PARENT, &nd);
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}
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if (err)
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goto out;
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dentry = lookup_create(&nd, 0);
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if (!IS_ERR(dentry)) {
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err = vfs_mknod(nd.path.dentry->d_inode,
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dentry, mode, dev->devt);
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if (!err) {
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struct iattr newattrs;
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/* fixup possibly umasked mode */
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newattrs.ia_mode = mode;
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newattrs.ia_valid = ATTR_MODE;
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mutex_lock(&dentry->d_inode->i_mutex);
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notify_change(dentry, &newattrs);
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mutex_unlock(&dentry->d_inode->i_mutex);
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/* mark as kernel-created inode */
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dentry->d_inode->i_private = &dev_mnt;
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}
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dput(dentry);
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} else {
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err = PTR_ERR(dentry);
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}
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mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
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path_put(&nd.path);
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out:
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kfree(tmp);
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revert_creds(curr_cred);
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return err;
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}
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static int dev_rmdir(const char *name)
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{
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struct nameidata nd;
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struct dentry *dentry;
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int err;
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err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,
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name, LOOKUP_PARENT, &nd);
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if (err)
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return err;
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mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
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dentry = lookup_one_len(nd.last.name, nd.path.dentry, nd.last.len);
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if (!IS_ERR(dentry)) {
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if (dentry->d_inode) {
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if (dentry->d_inode->i_private == &dev_mnt)
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err = vfs_rmdir(nd.path.dentry->d_inode,
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dentry);
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else
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err = -EPERM;
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} else {
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err = -ENOENT;
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}
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dput(dentry);
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} else {
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err = PTR_ERR(dentry);
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}
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mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
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path_put(&nd.path);
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return err;
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}
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static int delete_path(const char *nodepath)
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{
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const char *path;
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int err = 0;
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path = kstrdup(nodepath, GFP_KERNEL);
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if (!path)
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return -ENOMEM;
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mutex_lock(&dirlock);
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for (;;) {
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char *base;
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base = strrchr(path, '/');
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if (!base)
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break;
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base[0] = '\0';
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err = dev_rmdir(path);
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if (err)
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break;
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}
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mutex_unlock(&dirlock);
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kfree(path);
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return err;
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}
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static int dev_mynode(struct device *dev, struct inode *inode, struct kstat *stat)
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{
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/* did we create it */
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if (inode->i_private != &dev_mnt)
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return 0;
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/* does the dev_t match */
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if (is_blockdev(dev)) {
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if (!S_ISBLK(stat->mode))
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return 0;
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} else {
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if (!S_ISCHR(stat->mode))
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return 0;
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}
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if (stat->rdev != dev->devt)
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return 0;
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/* ours */
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return 1;
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}
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int devtmpfs_delete_node(struct device *dev)
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{
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const char *tmp = NULL;
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const char *nodename;
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const struct cred *curr_cred;
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struct nameidata nd;
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struct dentry *dentry;
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struct kstat stat;
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int deleted = 1;
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int err;
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if (!dev_mnt)
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return 0;
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nodename = device_get_devnode(dev, NULL, &tmp);
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if (!nodename)
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return -ENOMEM;
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curr_cred = override_creds(&init_cred);
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err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,
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nodename, LOOKUP_PARENT, &nd);
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if (err)
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goto out;
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mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
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dentry = lookup_one_len(nd.last.name, nd.path.dentry, nd.last.len);
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if (!IS_ERR(dentry)) {
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if (dentry->d_inode) {
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err = vfs_getattr(nd.path.mnt, dentry, &stat);
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if (!err && dev_mynode(dev, dentry->d_inode, &stat)) {
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struct iattr newattrs;
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/*
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* before unlinking this node, reset permissions
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* of possible references like hardlinks
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*/
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newattrs.ia_uid = 0;
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newattrs.ia_gid = 0;
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newattrs.ia_mode = stat.mode & ~0777;
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newattrs.ia_valid =
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ATTR_UID|ATTR_GID|ATTR_MODE;
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mutex_lock(&dentry->d_inode->i_mutex);
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notify_change(dentry, &newattrs);
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mutex_unlock(&dentry->d_inode->i_mutex);
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err = vfs_unlink(nd.path.dentry->d_inode,
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dentry);
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if (!err || err == -ENOENT)
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deleted = 1;
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}
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} else {
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err = -ENOENT;
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}
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dput(dentry);
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} else {
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err = PTR_ERR(dentry);
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}
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mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
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path_put(&nd.path);
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if (deleted && strchr(nodename, '/'))
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delete_path(nodename);
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out:
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kfree(tmp);
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revert_creds(curr_cred);
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return err;
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}
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/*
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* If configured, or requested by the commandline, devtmpfs will be
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* auto-mounted after the kernel mounted the root filesystem.
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*/
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int devtmpfs_mount(const char *mntdir)
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{
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int err;
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if (!dev_mount)
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return 0;
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if (!dev_mnt)
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return 0;
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err = sys_mount("devtmpfs", (char *)mntdir, "devtmpfs", MS_SILENT, NULL);
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if (err)
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printk(KERN_INFO "devtmpfs: error mounting %i\n", err);
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else
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printk(KERN_INFO "devtmpfs: mounted\n");
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return err;
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}
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/*
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* Create devtmpfs instance, driver-core devices will add their device
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* nodes here.
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*/
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int __init devtmpfs_init(void)
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{
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int err;
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struct vfsmount *mnt;
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char options[] = "mode=0755";
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err = register_filesystem(&dev_fs_type);
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if (err) {
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printk(KERN_ERR "devtmpfs: unable to register devtmpfs "
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"type %i\n", err);
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return err;
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}
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mnt = kern_mount_data(&dev_fs_type, options);
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if (IS_ERR(mnt)) {
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err = PTR_ERR(mnt);
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printk(KERN_ERR "devtmpfs: unable to create devtmpfs %i\n", err);
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unregister_filesystem(&dev_fs_type);
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return err;
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}
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dev_mnt = mnt;
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printk(KERN_INFO "devtmpfs: initialized\n");
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return 0;
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}
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