| #include <linux/export.h> |
| #include <linux/sched/signal.h> |
| #include <linux/sched/task.h> |
| #include <linux/fs.h> |
| #include <linux/path.h> |
| #include <linux/slab.h> |
| #include <linux/fs_struct.h> |
| #include "internal.h" |
| |
| /* |
| * Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values. |
| * It can block. |
| */ |
| void set_fs_root(struct fs_struct *fs, const struct path *path) |
| { |
| struct path old_root; |
| |
| path_get(path); |
| spin_lock(&fs->lock); |
| write_seqcount_begin(&fs->seq); |
| old_root = fs->root; |
| fs->root = *path; |
| write_seqcount_end(&fs->seq); |
| spin_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, const struct path *path) |
| { |
| struct path old_pwd; |
| |
| path_get(path); |
| spin_lock(&fs->lock); |
| write_seqcount_begin(&fs->seq); |
| old_pwd = fs->pwd; |
| fs->pwd = *path; |
| write_seqcount_end(&fs->seq); |
| spin_unlock(&fs->lock); |
| |
| if (old_pwd.dentry) |
| path_put(&old_pwd); |
| } |
| |
| static inline int replace_path(struct path *p, const struct path *old, const struct path *new) |
| { |
| if (likely(p->dentry != old->dentry || p->mnt != old->mnt)) |
| return 0; |
| *p = *new; |
| return 1; |
| } |
| |
| void chroot_fs_refs(const struct path *old_root, const 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) { |
| int hits = 0; |
| spin_lock(&fs->lock); |
| write_seqcount_begin(&fs->seq); |
| hits += replace_path(&fs->root, old_root, new_root); |
| hits += replace_path(&fs->pwd, old_root, new_root); |
| write_seqcount_end(&fs->seq); |
| while (hits--) { |
| count++; |
| path_get(new_root); |
| } |
| spin_unlock(&fs->lock); |
| } |
| task_unlock(p); |
| } while_each_thread(g, p); |
| read_unlock(&tasklist_lock); |
| while (count--) |
| path_put(old_root); |
| } |
| |
| void free_fs_struct(struct fs_struct *fs) |
| { |
| 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) { |
| int kill; |
| task_lock(tsk); |
| spin_lock(&fs->lock); |
| tsk->fs = NULL; |
| kill = !--fs->users; |
| spin_unlock(&fs->lock); |
| task_unlock(tsk); |
| if (kill) |
| free_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) { |
| fs->users = 1; |
| fs->in_exec = 0; |
| spin_lock_init(&fs->lock); |
| seqcount_init(&fs->seq); |
| fs->umask = old->umask; |
| |
| spin_lock(&old->lock); |
| fs->root = old->root; |
| path_get(&fs->root); |
| fs->pwd = old->pwd; |
| path_get(&fs->pwd); |
| spin_unlock(&old->lock); |
| } |
| return fs; |
| } |
| |
| int unshare_fs_struct(void) |
| { |
| struct fs_struct *fs = current->fs; |
| struct fs_struct *new_fs = copy_fs_struct(fs); |
| int kill; |
| |
| if (!new_fs) |
| return -ENOMEM; |
| |
| task_lock(current); |
| spin_lock(&fs->lock); |
| kill = !--fs->users; |
| current->fs = new_fs; |
| spin_unlock(&fs->lock); |
| task_unlock(current); |
| |
| if (kill) |
| free_fs_struct(fs); |
| |
| return 0; |
| } |
| EXPORT_SYMBOL_GPL(unshare_fs_struct); |
| |
| int current_umask(void) |
| { |
| return current->fs->umask; |
| } |
| EXPORT_SYMBOL(current_umask); |
| |
| /* to be mentioned only in INIT_TASK */ |
| struct fs_struct init_fs = { |
| .users = 1, |
| .lock = __SPIN_LOCK_UNLOCKED(init_fs.lock), |
| .seq = SEQCNT_ZERO(init_fs.seq), |
| .umask = 0022, |
| }; |