Re: [PATCH] detour TTY driver

From: Al Viro
Date: Sat May 29 2010 - 18:59:21 EST


On Sat, May 29, 2010 at 11:54:02PM +0100, Alan Cox wrote:
> > + /* re-register our fops write function */
> > + detour_fops.write = detour_write;
> > +
> > + detour_file.f_dentry = &detour_dentry;
> > + detour_file.f_dentry->d_inode = &detour_inode;
> > + detour_file.f_op = &detour_fops;
> > + detour_file.f_mode |= FMODE_WRITE;
> > + security_file_alloc(&detour_file);
> > + INIT_LIST_HEAD(&detour_file.f_u.fu_list);
> > +
> > + detour_inode.i_rdev = MKDEV(TTYAUX_MAJOR, 3);
> > + security_inode_alloc(&detour_inode);
> > + INIT_LIST_HEAD(&detour_inode.inotify_watches);
> > +
> > + ret = detour_fops.open(&detour_inode, &detour_file);
> > + printk(KERN_INFO "detour_fops.open() returned %ld\n", ret);
> > + ret = detour_fops.unlocked_ioctl(&detour_file, TIOCCONS, 0);
> > + printk(KERN_INFO "detour_fops.ioctl() returned %ld\n", ret);

That alone is enough for a NAK. Do Not Do That. Fake struct file/dentry/inode
and their uses are not acceptable. Neither is modifying file_operations,
while we are at it.
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