switch devtmpfs object creation/removal to separate kernel thread
... and give it a namespace where devtmpfs would be mounted on root, thus avoiding abuses of vfs_path_lookup() (it was never intended to be used with LOOKUP_PARENT). Games with credentials are also gone. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>hifive-unleashed-5.1
Al Viro
parent
6657719390
commit
2780f1ff6a
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@ -21,12 +21,11 @@
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#include <linux/fs.h>
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#include <linux/shmem_fs.h>
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#include <linux/ramfs.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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#include <linux/slab.h>
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#include <linux/kthread.h>
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static struct vfsmount *dev_mnt;
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static struct task_struct *thread;
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#if defined CONFIG_DEVTMPFS_MOUNT
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static int mount_dev = 1;
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@ -34,7 +33,16 @@ static int mount_dev = 1;
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static int mount_dev;
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#endif
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static DEFINE_MUTEX(dirlock);
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static DEFINE_SPINLOCK(req_lock);
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static struct req {
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struct req *next;
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struct completion done;
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int err;
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const char *name;
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mode_t mode; /* 0 => delete */
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struct device *dev;
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} *requests;
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static int __init mount_param(char *str)
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{
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@ -68,14 +76,79 @@ static inline int is_blockdev(struct device *dev)
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static inline int is_blockdev(struct device *dev) { return 0; }
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#endif
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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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struct req req;
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if (!thread)
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return 0;
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req.mode = 0;
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req.name = device_get_devnode(dev, &req.mode, &tmp);
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if (!req.name)
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return -ENOMEM;
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if (req.mode == 0)
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req.mode = 0600;
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if (is_blockdev(dev))
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req.mode |= S_IFBLK;
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else
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req.mode |= S_IFCHR;
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req.dev = dev;
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init_completion(&req.done);
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spin_lock(&req_lock);
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req.next = requests;
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requests = &req;
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spin_unlock(&req_lock);
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wake_up_process(thread);
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wait_for_completion(&req.done);
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kfree(tmp);
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return req.err;
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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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struct req req;
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if (!thread)
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return 0;
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req.name = device_get_devnode(dev, NULL, &tmp);
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if (!req.name)
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return -ENOMEM;
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req.mode = 0;
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req.dev = dev;
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init_completion(&req.done);
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spin_lock(&req_lock);
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req.next = requests;
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requests = &req;
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spin_unlock(&req_lock);
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wake_up_process(thread);
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wait_for_completion(&req.done);
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kfree(tmp);
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return req.err;
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}
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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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err = kern_path_parent(name, &nd);
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if (err)
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return err;
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@ -84,7 +157,7 @@ static int dev_mkdir(const char *name, mode_t mode)
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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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dentry->d_inode->i_private = &thread;
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dput(dentry);
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} else {
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err = PTR_ERR(dentry);
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@ -99,7 +172,6 @@ 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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@ -126,45 +198,22 @@ static int create_path(const char *nodepath)
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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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static int handle_create(const char *nodename, mode_t mode, 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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err = kern_path_parent(nodename, &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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err = kern_path_parent(nodename, &nd);
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}
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if (err)
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goto out;
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return err;
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dentry = lookup_create(&nd, 0);
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if (!IS_ERR(dentry)) {
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@ -181,7 +230,7 @@ int devtmpfs_create_node(struct device *dev)
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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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dentry->d_inode->i_private = &thread;
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}
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dput(dentry);
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} else {
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@ -190,9 +239,6 @@ int devtmpfs_create_node(struct device *dev)
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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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@ -202,8 +248,7 @@ static int dev_rmdir(const char *name)
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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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err = kern_path_parent(name, &nd);
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if (err)
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return err;
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@ -211,7 +256,7 @@ static int dev_rmdir(const char *name)
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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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if (dentry->d_inode->i_private == &thread)
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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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@ -238,7 +283,6 @@ static int delete_path(const char *nodepath)
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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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@ -250,7 +294,6 @@ static int delete_path(const char *nodepath)
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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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@ -259,7 +302,7 @@ static int delete_path(const char *nodepath)
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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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if (inode->i_private != &thread)
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return 0;
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/* does the dev_t match */
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@ -277,29 +320,17 @@ static int dev_mynode(struct device *dev, struct inode *inode, struct kstat *sta
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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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static int handle_remove(const char *nodename, 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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err = kern_path_parent(nodename, &nd);
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if (err)
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goto out;
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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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@ -337,9 +368,6 @@ int devtmpfs_delete_node(struct device *dev)
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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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@ -354,7 +382,7 @@ int devtmpfs_mount(const char *mntdir)
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if (!mount_dev)
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return 0;
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if (!dev_mnt)
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if (!thread)
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return 0;
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err = sys_mount("devtmpfs", (char *)mntdir, "devtmpfs", MS_SILENT, NULL);
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@ -365,31 +393,79 @@ int devtmpfs_mount(const char *mntdir)
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return err;
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}
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static __initdata DECLARE_COMPLETION(setup_done);
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static int handle(const char *name, mode_t mode, struct device *dev)
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{
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if (mode)
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return handle_create(name, mode, dev);
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else
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return handle_remove(name, dev);
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}
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static int devtmpfsd(void *p)
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{
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char options[] = "mode=0755";
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int *err = p;
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*err = sys_unshare(CLONE_NEWNS);
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if (*err)
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goto out;
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*err = sys_mount("devtmpfs", "/", "devtmpfs", MS_SILENT, options);
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if (*err)
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goto out;
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sys_chdir("/.."); /* will traverse into overmounted root */
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sys_chroot(".");
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complete(&setup_done);
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while (1) {
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spin_lock(&req_lock);
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while (requests) {
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struct req *req = requests;
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requests = NULL;
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spin_unlock(&req_lock);
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while (req) {
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req->err = handle(req->name, req->mode, req->dev);
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complete(&req->done);
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req = req->next;
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}
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spin_lock(&req_lock);
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}
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set_current_state(TASK_INTERRUPTIBLE);
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spin_unlock(&req_lock);
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schedule();
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__set_current_state(TASK_RUNNING);
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}
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return 0;
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out:
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complete(&setup_done);
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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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int 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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thread = kthread_run(devtmpfsd, &err, "kdevtmpfs");
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if (!IS_ERR(thread)) {
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wait_for_completion(&setup_done);
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} else {
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err = PTR_ERR(thread);
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thread = NULL;
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}
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if (err) {
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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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