On Wed, Aug 17, 2022 at 11:32 PM Greg KH gregkh@linuxfoundation.org wrote:
On Thu, Aug 18, 2022 at 08:26:38AM +0200, Greg KH wrote:
On Wed, Aug 17, 2022 at 02:47:25PM -0700, Axel Rasmussen wrote:
+static int userfaultfd_dev_open(struct inode *inode, struct file *file) +{
- return 0;
If your open does nothing, no need to list it here at all, right?
+}
+static long userfaultfd_dev_ioctl(struct file *file, unsigned int cmd, unsigned long flags) +{
- if (cmd != USERFAULTFD_IOC_NEW)
return -EINVAL;- return new_userfaultfd(flags);
+}
+static const struct file_operations userfaultfd_dev_fops = {
- .open = userfaultfd_dev_open,
- .unlocked_ioctl = userfaultfd_dev_ioctl,
- .compat_ioctl = userfaultfd_dev_ioctl,
Why do you need to set compat_ioctl? Shouldn't it just default to the existing one?
And why is this a device node at all? Shouldn't the syscall handle all of this (to be honest, I didn't read anything but the misc code, sorry.)
Ah, read the documentation now. Seems you want to make it easier for people to get permissions on a system. Doesn't seem wise, but hey, it's not my feature...
Thanks for taking a look Greg!
WIth the syscall, the only way to get access to this feature is to have CAP_SYS_PTRACE. Which gives you access to this, *plus* a bunch more stuff.
My basic goal is to grant access to just this feature by itself, not really just to make it easier to access. I think a device node is the simplest way to achieve that (see the cover letter for considered alternatives).
The other feedback looks like good simplification to me - I'll send another version with those changes. I have to admit this is the first time I've messed with misc device nodes, so apologies for being overly explicit. :)
thanks,
greg k-h