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#include <linux/module.h>
#include <linux/sched.h>
#include <linux/fs.h>
#include <linux/path.h>
#include <linux/slab.h>
/*
* Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values.
* It can block.
*/
void set_fs_root(struct fs_struct *fs, struct path *path)
{
struct path old_root;
write_lock(&fs->lock);
old_root = fs->root;
fs->root = *path;
path_get(path);
write_unlock(&fs->lock);
if (old_root.dentry)
path_put(&old_root);
}
/*
* Replace the fs->{pwdmnt,pwd} with {mnt,dentry}. Put the old values.
* It can block.
*/
void set_fs_pwd(struct fs_struct *fs, struct path *path)
{
struct path old_pwd;
write_lock(&fs->lock);
old_pwd = fs->pwd;
fs->pwd = *path;
path_get(path);
write_unlock(&fs->lock);
if (old_pwd.dentry)
path_put(&old_pwd);
}
void chroot_fs_refs(struct path *old_root, struct path *new_root)
{
struct task_struct *g, *p;
struct fs_struct *fs;
int count = 0;
read_lock(&tasklist_lock);
do_each_thread(g, p) {
task_lock(p);
fs = p->fs;
if (fs) {
write_lock(&fs->lock);
if (fs->root.dentry == old_root->dentry
&& fs->root.mnt == old_root->mnt) {
path_get(new_root);
fs->root = *new_root;
count++;
}
if (fs->pwd.dentry == old_root->dentry
&& fs->pwd.mnt == old_root->mnt) {
path_get(new_root);
fs->pwd = *new_root;
count++;
}
write_unlock(&fs->lock);
}
task_unlock(p);
} while_each_thread(g, p);
read_unlock(&tasklist_lock);
while (count--)
path_put(old_root);
}
void put_fs_struct(struct fs_struct *fs)
{
/* No need to hold fs->lock if we are killing it */
if (atomic_dec_and_test(&fs->count)) {
path_put(&fs->root);
path_put(&fs->pwd);
kmem_cache_free(fs_cachep, fs);
}
}
void exit_fs(struct task_struct *tsk)
{
struct fs_struct * fs = tsk->fs;
if (fs) {
task_lock(tsk);
tsk->fs = NULL;
task_unlock(tsk);
put_fs_struct(fs);
}
}
struct fs_struct *copy_fs_struct(struct fs_struct *old)
{
struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
/* We don't need to lock fs - think why ;-) */
if (fs) {
atomic_set(&fs->count, 1);
rwlock_init(&fs->lock);
fs->umask = old->umask;
read_lock(&old->lock);
fs->root = old->root;
path_get(&old->root);
fs->pwd = old->pwd;
path_get(&old->pwd);
read_unlock(&old->lock);
}
return fs;
}
int unshare_fs_struct(void)
{
struct fs_struct *fsp = copy_fs_struct(current->fs);
if (!fsp)
return -ENOMEM;
exit_fs(current);
current->fs = fsp;
return 0;
}
EXPORT_SYMBOL_GPL(unshare_fs_struct);
/* to be mentioned only in INIT_TASK */
struct fs_struct init_fs = {
.count = ATOMIC_INIT(1),
.lock = __RW_LOCK_UNLOCKED(init_fs.lock),
.umask = 0022,
};
void daemonize_fs_struct(void)
{
struct fs_struct *fs;
exit_fs(current); /* current->fs->count--; */
fs = &init_fs;
current->fs = fs;
atomic_inc(&fs->count);
}
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