On Wed, Oct 11, 2023 at 5:09 AM Chuyi Zhou <zhouchuyi@xxxxxxxxxxxxx> wrote: > > css_iter and task_iter should be used in rcu section. Specifically, in > sleepable progs explicit bpf_rcu_read_lock() is needed before use these > iters. In normal bpf progs that have implicit rcu_read_lock(), it's OK to > use them directly. > > This patch adds a new a KF flag KF_RCU_PROTECTED for bpf_iter_task_new and > bpf_iter_css_new. It means the kfunc should be used in RCU CS. We check > whether we are in rcu cs before we want to invoke this kfunc. If the rcu > protection is guaranteed, we would let st->type = PTR_TO_STACK | MEM_RCU. > Once user do rcu_unlock during the iteration, state MEM_RCU of regs would > be cleared. is_iter_reg_valid_init() will reject if reg->type is UNTRUSTED. > > It is worth noting that currently, bpf_rcu_read_unlock does not > clear the state of the STACK_ITER reg, since bpf_for_each_spilled_reg > only considers STACK_SPILL. This patch also let bpf_for_each_spilled_reg > search STACK_ITER. > > Signed-off-by: Chuyi Zhou <zhouchuyi@xxxxxxxxxxxxx> > --- > include/linux/bpf_verifier.h | 19 ++++++++------ > include/linux/btf.h | 1 + > kernel/bpf/helpers.c | 4 +-- > kernel/bpf/verifier.c | 50 ++++++++++++++++++++++++++++-------- > 4 files changed, 53 insertions(+), 21 deletions(-) > LGTM. Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>