On Mon, Jan 11, 2021 at 7:57 PM Martin KaFai Lau <ka...@fb.com> wrote:
>
> On Fri, Jan 08, 2021 at 03:19:47PM -0800, Song Liu wrote:
>
> [ ... ]
>
> > diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c
> > index dd5aedee99e73..9bd47ad2b26f1 100644
> > --- a/kernel/bpf/bpf_local_storage.c
> > +++ b/kernel/bpf/bpf_local_storage.c
> > @@ -140,17 +140,18 @@ static void __bpf_selem_unlink_storage(struct
> > bpf_local_storage_elem *selem)
> > {
> > struct bpf_local_storage *local_storage;
> > bool free_local_storage = false;
> > + unsigned long flags;
> >
> > if (unlikely(!selem_linked_to_storage(selem)))
> > /* selem has already been unlinked from sk */
> > return;
> >
> > local_storage = rcu_dereference(selem->local_storage);
> > - raw_spin_lock_bh(&local_storage->lock);
> > + raw_spin_lock_irqsave(&local_storage->lock, flags);
> It will be useful to have a few words in commit message on this change
> for future reference purpose.
>
> Please also remove the in_irq() check from bpf_sk_storage.c
> to avoid confusion in the future. It probably should
> be in a separate patch.
>
> [ ... ]
>
> > diff --git a/kernel/bpf/bpf_task_storage.c b/kernel/bpf/bpf_task_storage.c
> > index 4ef1959a78f27..f654b56907b69 100644
> > diff --git a/kernel/fork.c b/kernel/fork.c
> > index 7425b3224891d..3d65c8ebfd594 100644
> [ ... ]
>
> > --- a/kernel/fork.c
> > +++ b/kernel/fork.c
> > @@ -96,6 +96,7 @@
> > #include <linux/kasan.h>
> > #include <linux/scs.h>
> > #include <linux/io_uring.h>
> > +#include <linux/bpf.h>
> >
> > #include <asm/pgalloc.h>
> > #include <linux/uaccess.h>
> > @@ -734,6 +735,7 @@ void __put_task_struct(struct task_struct *tsk)
> > cgroup_free(tsk);
> > task_numa_free(tsk, true);
> > security_task_free(tsk);
> > + bpf_task_storage_free(tsk);
> > exit_creds(tsk);
> If exit_creds() is traced by a bpf and this bpf is doing
> bpf_task_storage_get(..., BPF_LOCAL_STORAGE_GET_F_CREATE),
> new task storage will be created after bpf_task_storage_free().
>
> I recalled there was an earlier discussion with KP and KP mentioned
> BPF_LSM will not be called with a task that is going away.
> It seems enabling bpf task storage in bpf tracing will break
> this assumption and needs to be addressed?
For tracing programs, I think we will need an allow list where
task local storage can be used.
