Re: [RFC PATCH 2/3] add statmnt(2) syscall

[Christian Brauner <brauner@kernel.org>]

On Tue, Sep 19, 2023 at 02:59:53PM +0200, Miklos Szeredi wrote:
> On Tue, 19 Sept 2023 at 14:41, Christian Brauner <brauner@kernel.org> wrote:
> >
> > > >  with __u32 size for mnt_root and mnt_point
> > >
> > > Unnecessary if the strings are nul terminated.
> >
> > All ok by me so far but how does the kernel know the size of the buffer
> > to copy into? Wouldn't it be better to allow userspace to specify that?
> > I'm probably just missing something but I better ask.
> 
> Because size of the buffer is given as the syscall argument.
> 
>   long statmount(u64 mnt_id, u64 mask, struct statmnt __user *buf,
> size_t bufsize, unsigned int flags);
> 
> If you are still hung up about this not being properly typed, how about this:

I really just wasn't clear how exactly you envisioned this. Your
proposal as is sounds good to me! I'm on board. I prefer the two offsets
as that lets us avoid searching for null bytes. So please leave it as is!
Thanks!