[dpdk-dev] [PATCH] Fix `eventfd_link' module leakages and races
Pavel Boldin
pboldin at mirantis.com
Fri Mar 20 16:57:30 CET 2015
Changchun,
Please review the updated patch.
Pavel
On Tue, Mar 17, 2015 at 3:29 AM, Ouyang, Changchun <
changchun.ouyang at intel.com> wrote:
>
>
> > -----Original Message-----
> > From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Pavel Boldin
> > Sent: Tuesday, March 17, 2015 12:41 AM
> > To: dev at dpdk.org
> > Cc: Pavel Boldin
> > Subject: [dpdk-dev] [PATCH] Fix `eventfd_link' module leakages and races
> >
> > From: Pavel Boldin <pboldin at mirantis.com>
> >
> > The `eventfd_link' module provides an API to "steal" fd from another
> process
> > had been written with a bug that leaks `struct file' because of the extra
> > reference counter increment and missing `fput' call.
> >
> > The other bug is using another process' `task_struct' without
> incrementing a
> > reference counter.
> >
> > Fix these bugs and refactor the module.
> > ---
> > examples/vhost/eventfd_link/eventfd_link.c | 236 ++++++++++++++++-----
> > --------
> > 1 file changed, 130 insertions(+), 106 deletions(-)
> >
> > diff --git a/examples/vhost/eventfd_link/eventfd_link.c
> > b/examples/vhost/eventfd_link/eventfd_link.c
> > index 69470ba..9f1f8fb 100644
> > --- a/examples/vhost/eventfd_link/eventfd_link.c
> > +++ b/examples/vhost/eventfd_link/eventfd_link.c
> > @@ -42,15 +42,15 @@
> > * get_files_struct is copied from fs/file.c
> > */
> > struct files_struct *
> > -get_files_struct (struct task_struct *task)
> > +get_files_struct(struct task_struct *task)
> > {
> > struct files_struct *files;
> >
> > - task_lock (task);
> > + task_lock(task);
> > files = task->files;
> > if (files)
> > - atomic_inc (&files->count);
> > - task_unlock (task);
> > + atomic_inc(&files->count);
> > + task_unlock(task);
>
> I don't find any actual code change for above.
> If they are tab, space, indent refine,
> I suggest it needs a separate patch named code cleanup,
> Then it is easy to review.
>
> Same for other places.
>
> Done.
> Changchun
>
>
> >
> > return files;
> > }
> > @@ -59,117 +59,142 @@ get_files_struct (struct task_struct *task)
> > * put_files_struct is extracted from fs/file.c
> > */
> > void
> > -put_files_struct (struct files_struct *files)
> > +put_files_struct(struct files_struct *files)
> > {
> > - if (atomic_dec_and_test (&files->count))
> > - {
> > + if (atomic_dec_and_test(&files->count))
> > BUG ();
> > +}
> > +
> > +static struct file *
> > +fget_from_files(struct files_struct *files, unsigned fd) {
> > + struct file *file;
> > +
> > + rcu_read_lock();
> > + file = fcheck_files(files, fd);
> > + if (file)
> > + {
> > + if (file->f_mode & FMODE_PATH
> > + || !atomic_long_inc_not_zero(&file->f_count))
> > + file = NULL;
> > }
> > + rcu_read_unlock();
> > +
> > + return file;
> > +}
> > +
> > +static int
> > +close_fd(unsigned fd)
> > +{
> > + struct file *file;
> > + struct files_struct *files = current->files;
> > + struct fdtable *fdt;
> > +
> > + spin_lock(&files->file_lock);
> > + fdt = files_fdtable(files);
> > + if (fd >= fdt->max_fds)
> > + goto out_unlock;
> > + file = fdt->fd[fd];
> > + if (!file)
> > + goto out_unlock;
> > + rcu_assign_pointer(fdt->fd[fd], NULL);
> > + __clear_bit(fd, fdt->close_on_exec);
> > + spin_unlock(&files->file_lock);
> > + return filp_close(file, files);
> > +
> > +out_unlock:
> > + spin_unlock(&files->file_lock);
> > + return -EBADF;
> > }
> >
> >
> > static long
> > -eventfd_link_ioctl (struct file *f, unsigned int ioctl, unsigned long
> arg)
> > +eventfd_link_ioctl_copy(unsigned long arg)
> > {
> > - void __user *argp = (void __user *) arg;
> > + long ret = -EFAULT;
> > struct task_struct *task_target = NULL;
> > - struct file *file;
> > - struct files_struct *files;
> > - struct fdtable *fdt;
> > + struct file *target_file = NULL;
> > + struct files_struct *target_files = NULL;
> > struct eventfd_copy eventfd_copy;
> > + struct pid *pid;
> > +
> > + if (copy_from_user(&eventfd_copy, (void __user*)arg,
> > + sizeof(struct eventfd_copy)))
> > + goto out;
> > +
> > + /*
> > + * Find the task struct for the target pid
> > + */
> > + pid = find_vpid(eventfd_copy.target_pid);
> > + if (pid == NULL) {
> > + printk(KERN_INFO "Unable to find pid %d\n",
> > + eventfd_copy.target_pid);
> > + goto out;
> > + }
> > +
> > + task_target = get_pid_task(pid, PIDTYPE_PID);
> > + if (task_target == NULL) {
> > + printk(KERN_INFO "Failed to get task for pid %d\n",
> > + eventfd_copy.target_pid);
> > + goto out;
> > + }
> > +
> > + ret = close_fd(eventfd_copy.source_fd);
> > + if (ret)
> > + goto out_task;
> > + ret = -EFAULT;
> > +
> > + /*
> > + * Find the file struct associated with the target fd.
> > + */
> > +
> > + target_files = get_files_struct(task_target);
> > + if (target_files == NULL) {
> > + printk (KERN_INFO "Failed to get target files struct\n");
> > + goto out_task;
> > + }
> > +
> > + target_file = fget_from_files(target_files,
> eventfd_copy.target_fd);
> > +
> > + if (target_file == NULL) {
> > + printk (KERN_INFO "Failed to get file from target pid\n");
> > + goto out_target_files;
> > + }
> > +
> > +
> > + /*
> > + * Install the file struct from the target process into the
> > + * file desciptor of the source process,
> > + */
> > +
> > + fd_install(eventfd_copy.source_fd, target_file);
> > +
> > + ret = 0;
> > +
> > +out_target_files:
> > + put_files_struct(target_files);
> > +out_task:
> > + put_task_struct(task_target);
> > +out:
> > + return ret;
> > +}
> > +
> > +static long
> > +eventfd_link_ioctl(struct file *f, unsigned int ioctl, unsigned long
> > +arg) {
> > + long ret;
> >
> > switch (ioctl)
> > {
> > case EVENTFD_COPY:
> > - if (copy_from_user (&eventfd_copy, argp, sizeof
> > (struct eventfd_copy)))
> > - return -EFAULT;
> > -
> > - /*
> > - * Find the task struct for the target pid
> > - */
> > - task_target =
> > - pid_task (find_vpid
> > (eventfd_copy.target_pid), PIDTYPE_PID);
> > - if (task_target == NULL)
> > - {
> > - printk (KERN_DEBUG "Failed to get mem ctx
> > for target pid\n");
> > - return -EFAULT;
> > - }
> > -
> > - files = get_files_struct (current);
> > - if (files == NULL)
> > - {
> > - printk (KERN_DEBUG "Failed to get files
> > struct\n");
> > - return -EFAULT;
> > - }
> > -
> > - rcu_read_lock ();
> > - file = fcheck_files (files,
> eventfd_copy.source_fd);
> > - if (file)
> > - {
> > - if (file->f_mode & FMODE_PATH
> > -
> > || !atomic_long_inc_not_zero (&file->f_count))
> > - file = NULL;
> > - }
> > - rcu_read_unlock ();
> > - put_files_struct (files);
> > -
> > - if (file == NULL)
> > - {
> > - printk (KERN_DEBUG "Failed to get file from
> > source pid\n");
> > - return 0;
> > - }
> > -
> > - /*
> > - * Release the existing eventfd in the source
> process
> > - */
> > - spin_lock (&files->file_lock);
> > - fput(file);
> > - filp_close (file, files);
> > - fdt = files_fdtable (files);
> > - fdt->fd[eventfd_copy.source_fd] = NULL;
> > - spin_unlock (&files->file_lock);
> > -
> > - /*
> > - * Find the file struct associated with the target
> fd.
> > - */
> > -
> > - files = get_files_struct (task_target);
> > - if (files == NULL)
> > - {
> > - printk (KERN_DEBUG "Failed to get files
> > struct\n");
> > - return -EFAULT;
> > - }
> > -
> > - rcu_read_lock ();
> > - file = fcheck_files (files,
> eventfd_copy.target_fd);
> > - if (file)
> > - {
> > - if (file->f_mode & FMODE_PATH
> > -
> > || !atomic_long_inc_not_zero (&file->f_count))
> > - file = NULL;
> > - }
> > - rcu_read_unlock ();
> > - put_files_struct (files);
> > -
> > - if (file == NULL)
> > - {
> > - printk (KERN_DEBUG "Failed to get file from
> > target pid\n");
> > - return 0;
> > - }
> > -
> > -
> > - /*
> > - * Install the file struct from the target process
> into
> > the
> > - * file desciptor of the source process,
> > - */
> > -
> > - fd_install (eventfd_copy.source_fd, file);
> > -
> > - return 0;
> > -
> > + ret = eventfd_link_ioctl_copy(arg);
> > + break;
> > default:
> > - return -ENOIOCTLCMD;
> > + ret = -ENOIOCTLCMD;
> > + break;
> > }
> > +
> > + return ret;
> > }
> >
> > static const struct file_operations eventfd_link_fops = { @@ -184,21
> +209,20
> > @@ static struct miscdevice eventfd_link_misc = { };
> >
> > static int __init
> > -eventfd_link_init (void)
> > +eventfd_link_init(void)
> > {
> > - printk(KERN_INFO "eventfd_link is broken, use it at your risk\n");
> > - return misc_register (&eventfd_link_misc);
> > + return misc_register(&eventfd_link_misc);
> > }
> >
> > -module_init (eventfd_link_init);
> > +module_init(eventfd_link_init);
> >
> > static void __exit
> > -eventfd_link_exit (void)
> > +eventfd_link_exit(void)
> > {
> > - misc_deregister (&eventfd_link_misc);
> > + misc_deregister(&eventfd_link_misc);
> > }
> >
> > -module_exit (eventfd_link_exit);
> > +module_exit(eventfd_link_exit);
> >
> > MODULE_VERSION ("0.0.1");
> > MODULE_LICENSE ("GPL v2");
> > --
> > 1.9.1
>
>
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