| Message ID | 6-v3-402a7d6459de+24b-iommufd_jgg@nvidia.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | IOMMUFD Generic interface | expand |
> From: Jason Gunthorpe <jgg@nvidia.com> > Sent: Wednesday, October 26, 2022 2:12 AM > > 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. > > Signed-off-by: Jason Gunthorpe <jgg@nvidia.com> Reviewed-by: Kevin Tian <kevin.tian@intel.com>
diff --git a/include/linux/sched/user.h b/include/linux/sched/user.h index f054d0360a7533..4cc52698e214e2 100644 --- a/include/linux/sched/user.h +++ b/include/linux/sched/user.h @@ -25,7 +25,7 @@ struct user_struct { #if defined(CONFIG_PERF_EVENTS) || defined(CONFIG_BPF_SYSCALL) || \ defined(CONFIG_NET) || defined(CONFIG_IO_URING) || \ - defined(CONFIG_VFIO_PCI_ZDEV_KVM) + defined(CONFIG_VFIO_PCI_ZDEV_KVM) || IS_ENABLED(CONFIG_IOMMUFD) atomic_long_t locked_vm; #endif #ifdef CONFIG_WATCH_QUEUE diff --git a/kernel/user.c b/kernel/user.c index e2cf8c22b539a7..d667debeafd609 100644 --- a/kernel/user.c +++ b/kernel/user.c @@ -185,6 +185,7 @@ void free_uid(struct user_struct *up) if (refcount_dec_and_lock_irqsave(&up->__count, &uidhash_lock, &flags)) free_user(up, flags); } +EXPORT_SYMBOL_GPL(free_uid); struct user_struct *alloc_uid(kuid_t uid) {
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. Signed-off-by: Jason Gunthorpe <jgg@nvidia.com> --- include/linux/sched/user.h | 2 +- kernel/user.c | 1 + 2 files changed, 2 insertions(+), 1 deletion(-)