On Tue, Nov 29, 2022 at 04:48:16PM -0400, Jason Gunthorpe wrote: > On Tue, Nov 29, 2022 at 03:42:23PM -0500, Michael S. Tsirkin wrote: > > On Tue, Nov 29, 2022 at 04:29:30PM -0400, Jason Gunthorpe wrote: > > > Following the pattern of io_uring, perf, skb, and bpf, iommfd will use > > > user->locked_vm for accounting pinned pages. Ensure the value is included > > > in the struct and export free_uid() as iommufd is modular. > > > > > > user->locked_vm is the good accounting to use for ulimit because it is > > > per-user, and the security sandboxing of locked pages is not supposed to > > > be per-process. Other places (vfio, vdpa and infiniband) have used > > > mm->pinned_vm and/or mm->locked_vm for accounting pinned pages, but this > > > is only per-process and inconsistent with the new FOLL_LONGTERM users in > > > the kernel. > > > > > > Concurrent work is underway to try to put this in a cgroup, so everything > > > can be consistent and the kernel can provide a FOLL_LONGTERM limit that > > > actually provides security. > > > > > > Tested-by: Nicolin Chen <nicolinc@xxxxxxxxxx> > > > Tested-by: Yi Liu <yi.l.liu@xxxxxxxxx> > > > Tested-by: Lixiao Yang <lixiao.yang@xxxxxxxxx> > > > Tested-by: Matthew Rosato <mjrosato@xxxxxxxxxxxxx> > > > Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx> > > > Reviewed-by: Eric Auger <eric.auger@xxxxxxxxxx> > > > Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx> > > > > Just curious: why does the subject say "user::locked_vm"? As opposed to > > user->locked_vm? Made me think it's somehow related to rust in kernel or > > whatever. > > :: is the C++ way to say "member of a type", I suppose it is a typo > and should be user_struct::locked_vm > > The use of -> otherwise was to have some clarity about mm vs user > structs. > > Jason I note that commit log says user->locked_vm and that's clear enough IMHO, I'd leave C++ alone - IIRC yes you can write ptr->type::field but no one does so it's not idiomatic, :: is more commonly used with static members there. So this confuses more than it clarifies. But whatever, hardly a blocker. Feel free to ignore. -- MST
