169 lines
3.4 KiB
C
169 lines
3.4 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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#include <linux/export.h>
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#include <linux/sched/signal.h>
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#include <linux/sched/task.h>
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#include <linux/fs.h>
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#include <linux/path.h>
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#include <linux/slab.h>
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#include <linux/fs_struct.h>
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#include "internal.h"
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/*
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* Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values.
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* It can block.
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*/
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void set_fs_root(struct fs_struct *fs, const struct path *path)
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{
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struct path old_root;
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path_get(path);
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spin_lock(&fs->lock);
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write_seqcount_begin(&fs->seq);
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old_root = fs->root;
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fs->root = *path;
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write_seqcount_end(&fs->seq);
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spin_unlock(&fs->lock);
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if (old_root.dentry)
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path_put(&old_root);
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}
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/*
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* Replace the fs->{pwdmnt,pwd} with {mnt,dentry}. Put the old values.
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* It can block.
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*/
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void set_fs_pwd(struct fs_struct *fs, const struct path *path)
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{
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struct path old_pwd;
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path_get(path);
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spin_lock(&fs->lock);
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write_seqcount_begin(&fs->seq);
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old_pwd = fs->pwd;
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fs->pwd = *path;
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write_seqcount_end(&fs->seq);
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spin_unlock(&fs->lock);
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if (old_pwd.dentry)
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path_put(&old_pwd);
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}
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static inline int replace_path(struct path *p, const struct path *old, const struct path *new)
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{
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if (likely(p->dentry != old->dentry || p->mnt != old->mnt))
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return 0;
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*p = *new;
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return 1;
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}
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void chroot_fs_refs(const struct path *old_root, const struct path *new_root)
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{
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struct task_struct *g, *p;
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struct fs_struct *fs;
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int count = 0;
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read_lock(&tasklist_lock);
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do_each_thread(g, p) {
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task_lock(p);
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fs = p->fs;
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if (fs) {
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int hits = 0;
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spin_lock(&fs->lock);
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write_seqcount_begin(&fs->seq);
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hits += replace_path(&fs->root, old_root, new_root);
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hits += replace_path(&fs->pwd, old_root, new_root);
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write_seqcount_end(&fs->seq);
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while (hits--) {
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count++;
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path_get(new_root);
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}
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spin_unlock(&fs->lock);
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}
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task_unlock(p);
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} while_each_thread(g, p);
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read_unlock(&tasklist_lock);
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while (count--)
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path_put(old_root);
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}
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void free_fs_struct(struct fs_struct *fs)
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{
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path_put(&fs->root);
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path_put(&fs->pwd);
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kmem_cache_free(fs_cachep, fs);
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}
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void exit_fs(struct task_struct *tsk)
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{
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struct fs_struct *fs = tsk->fs;
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if (fs) {
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int kill;
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task_lock(tsk);
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spin_lock(&fs->lock);
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tsk->fs = NULL;
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kill = !--fs->users;
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spin_unlock(&fs->lock);
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task_unlock(tsk);
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if (kill)
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free_fs_struct(fs);
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}
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}
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struct fs_struct *copy_fs_struct(struct fs_struct *old)
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{
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struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
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/* We don't need to lock fs - think why ;-) */
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if (fs) {
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fs->users = 1;
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fs->in_exec = 0;
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spin_lock_init(&fs->lock);
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seqcount_spinlock_init(&fs->seq, &fs->lock);
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fs->umask = old->umask;
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spin_lock(&old->lock);
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fs->root = old->root;
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path_get(&fs->root);
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fs->pwd = old->pwd;
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path_get(&fs->pwd);
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spin_unlock(&old->lock);
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}
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return fs;
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}
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int unshare_fs_struct(void)
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{
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struct fs_struct *fs = current->fs;
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struct fs_struct *new_fs = copy_fs_struct(fs);
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int kill;
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if (!new_fs)
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return -ENOMEM;
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task_lock(current);
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spin_lock(&fs->lock);
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kill = !--fs->users;
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current->fs = new_fs;
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spin_unlock(&fs->lock);
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task_unlock(current);
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if (kill)
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free_fs_struct(fs);
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return 0;
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}
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EXPORT_SYMBOL_GPL(unshare_fs_struct);
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int current_umask(void)
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{
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return current->fs->umask;
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}
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EXPORT_SYMBOL(current_umask);
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/* to be mentioned only in INIT_TASK */
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struct fs_struct init_fs = {
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.users = 1,
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.lock = __SPIN_LOCK_UNLOCKED(init_fs.lock),
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.seq = SEQCNT_SPINLOCK_ZERO(init_fs.seq, &init_fs.lock),
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.umask = 0022,
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};
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