![Jann Horn](/assets/img/avatar_default.png)
This prevents users from triggering a stack overflow through a recursive invocation of pagefault handling that involves mapping procfs files into virtual memory. Signed-off-by: Jann Horn <jannh@google.com> Acked-by: Tyler Hicks <tyhicks@canonical.com> Cc: stable@vger.kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
182 lines
5.1 KiB
C
182 lines
5.1 KiB
C
/**
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* eCryptfs: Linux filesystem encryption layer
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*
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* Copyright (C) 2008 International Business Machines Corp.
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* Author(s): Michael A. Halcrow <mahalcro@us.ibm.com>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of the
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* License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
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* 02111-1307, USA.
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*/
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#include <linux/kthread.h>
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#include <linux/freezer.h>
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#include <linux/slab.h>
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#include <linux/wait.h>
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#include <linux/mount.h>
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#include <linux/file.h>
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#include "ecryptfs_kernel.h"
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struct ecryptfs_open_req {
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struct file **lower_file;
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struct path path;
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struct completion done;
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struct list_head kthread_ctl_list;
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};
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static struct ecryptfs_kthread_ctl {
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#define ECRYPTFS_KTHREAD_ZOMBIE 0x00000001
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u32 flags;
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struct mutex mux;
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struct list_head req_list;
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wait_queue_head_t wait;
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} ecryptfs_kthread_ctl;
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static struct task_struct *ecryptfs_kthread;
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/**
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* ecryptfs_threadfn
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* @ignored: ignored
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*
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* The eCryptfs kernel thread that has the responsibility of getting
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* the lower file with RW permissions.
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*
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* Returns zero on success; non-zero otherwise
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*/
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static int ecryptfs_threadfn(void *ignored)
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{
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set_freezable();
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while (1) {
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struct ecryptfs_open_req *req;
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wait_event_freezable(
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ecryptfs_kthread_ctl.wait,
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(!list_empty(&ecryptfs_kthread_ctl.req_list)
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|| kthread_should_stop()));
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mutex_lock(&ecryptfs_kthread_ctl.mux);
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if (ecryptfs_kthread_ctl.flags & ECRYPTFS_KTHREAD_ZOMBIE) {
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mutex_unlock(&ecryptfs_kthread_ctl.mux);
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goto out;
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}
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while (!list_empty(&ecryptfs_kthread_ctl.req_list)) {
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req = list_first_entry(&ecryptfs_kthread_ctl.req_list,
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struct ecryptfs_open_req,
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kthread_ctl_list);
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list_del(&req->kthread_ctl_list);
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*req->lower_file = dentry_open(&req->path,
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(O_RDWR | O_LARGEFILE), current_cred());
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complete(&req->done);
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}
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mutex_unlock(&ecryptfs_kthread_ctl.mux);
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}
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out:
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return 0;
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}
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int __init ecryptfs_init_kthread(void)
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{
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int rc = 0;
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mutex_init(&ecryptfs_kthread_ctl.mux);
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init_waitqueue_head(&ecryptfs_kthread_ctl.wait);
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INIT_LIST_HEAD(&ecryptfs_kthread_ctl.req_list);
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ecryptfs_kthread = kthread_run(&ecryptfs_threadfn, NULL,
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"ecryptfs-kthread");
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if (IS_ERR(ecryptfs_kthread)) {
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rc = PTR_ERR(ecryptfs_kthread);
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printk(KERN_ERR "%s: Failed to create kernel thread; rc = [%d]"
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"\n", __func__, rc);
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}
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return rc;
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}
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void ecryptfs_destroy_kthread(void)
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{
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struct ecryptfs_open_req *req, *tmp;
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mutex_lock(&ecryptfs_kthread_ctl.mux);
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ecryptfs_kthread_ctl.flags |= ECRYPTFS_KTHREAD_ZOMBIE;
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list_for_each_entry_safe(req, tmp, &ecryptfs_kthread_ctl.req_list,
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kthread_ctl_list) {
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list_del(&req->kthread_ctl_list);
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*req->lower_file = ERR_PTR(-EIO);
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complete(&req->done);
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}
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mutex_unlock(&ecryptfs_kthread_ctl.mux);
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kthread_stop(ecryptfs_kthread);
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wake_up(&ecryptfs_kthread_ctl.wait);
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}
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/**
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* ecryptfs_privileged_open
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* @lower_file: Result of dentry_open by root on lower dentry
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* @lower_dentry: Lower dentry for file to open
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* @lower_mnt: Lower vfsmount for file to open
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*
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* This function gets a r/w file opened againt the lower dentry.
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*
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* Returns zero on success; non-zero otherwise
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*/
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int ecryptfs_privileged_open(struct file **lower_file,
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struct dentry *lower_dentry,
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struct vfsmount *lower_mnt,
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const struct cred *cred)
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{
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struct ecryptfs_open_req req;
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int flags = O_LARGEFILE;
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int rc = 0;
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init_completion(&req.done);
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req.lower_file = lower_file;
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req.path.dentry = lower_dentry;
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req.path.mnt = lower_mnt;
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/* Corresponding dput() and mntput() are done when the
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* lower file is fput() when all eCryptfs files for the inode are
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* released. */
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flags |= IS_RDONLY(d_inode(lower_dentry)) ? O_RDONLY : O_RDWR;
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(*lower_file) = dentry_open(&req.path, flags, cred);
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if (!IS_ERR(*lower_file))
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goto have_file;
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if ((flags & O_ACCMODE) == O_RDONLY) {
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rc = PTR_ERR((*lower_file));
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goto out;
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}
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mutex_lock(&ecryptfs_kthread_ctl.mux);
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if (ecryptfs_kthread_ctl.flags & ECRYPTFS_KTHREAD_ZOMBIE) {
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rc = -EIO;
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mutex_unlock(&ecryptfs_kthread_ctl.mux);
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printk(KERN_ERR "%s: We are in the middle of shutting down; "
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"aborting privileged request to open lower file\n",
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__func__);
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goto out;
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}
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list_add_tail(&req.kthread_ctl_list, &ecryptfs_kthread_ctl.req_list);
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mutex_unlock(&ecryptfs_kthread_ctl.mux);
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wake_up(&ecryptfs_kthread_ctl.wait);
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wait_for_completion(&req.done);
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if (IS_ERR(*lower_file)) {
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rc = PTR_ERR(*lower_file);
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goto out;
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}
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have_file:
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if ((*lower_file)->f_op->mmap == NULL) {
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fput(*lower_file);
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*lower_file = NULL;
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rc = -EMEDIUMTYPE;
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}
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out:
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return rc;
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}
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