On Thu, Dec 07, 2023 at 04:43:03PM +0100, Arnd Bergmann wrote:

On Thu, Dec 7, 2023, at 15:58, Gregory Price wrote:

quoted

On Thu, Dec 07, 2023 at 08:13:22AM +0100, Arnd Bergmann wrote:

quoted

On Thu, Dec 7, 2023, at 01:27, Gregory Price wrote:

Aside from this, you should avoid holes in the data structure.
On 64-bit architectures, the layout above has holes after
policy_node and after addr_node.

      Arnd

doh, clearly i didn't stop to think about alignment. Good eye.
I'll redo this with __u/s members and fix the holes.

Didn't stop to think about compat pointers.  I don't think the
u64_to_user_ptr pattern is offensive, so i'll make that change.
At least I don't see what the other options are beyond compat.

Ok, sounds good.

I see you already call wrappers for compat mode to convert
iovec and nodemask layouts for the indirect pointers, and they
look correct. If you wanted to do handle the compat syscalls
using the same entry point, you could add the same kind of
helper to copy the mempolicy args from user space with an
optional conversion, but not having to do this is clearly
easier.

     Arnd

I don't know that either is easier, it's basically just what annoying
way do you want to handle this annoying problem.  I'll poke at it
and decide which one I hate less.

One thing i didn't really think about, probably the iovec/len
fields should just be args for mbind2, rather than embedded in
mpol_args - since mpol_args is supposed to describe the mpol
while the iovec/len describes what it applies to.

Simplifies the mpol_args structure a bit. Doesn't change the handling
at all. (bit of a rubber ducky comment here)

As always, I appreciate the input

~Gregory