[bpf,v3,0/2] bpf: fix a couple of issues with syscall program

Message

Yonghong Song Aug. 9, 2021, 11:51 p.m. UTC

syzbot ([1]) reported a rcu warning for syscall program when
bpf_get_current_cgroup_id() is called in the program. The
bpf_get_current_cgroup_id() helper expects cgroup related
mutex or rcu_read_lock(). The sleepable program cannot be
protected with rcu read_lock, hence the warning.

To fix the problem, Patch 1 added rcu_read_lock() in
affected helpers, and Patch 2 added missing
bpf_read_lock_trace() for syscall type of bpf programs.

 [1] https://lore.kernel.org/bpf/[e-mail]/

Changelog:
  v2 -> v3:
    - use rcu_read_lock() protection for
      bpf_get_current_[ancestor_]cgroup_id() helper.
  v1 -> v2:
    - use bpf_read_lock_trace() instead of bpf_read_lock() for
      bpf_prog_run_pin_on_cpu().
    - disallow bpf_get_current_[ancestor_]cgroup_id() helper.

Yonghong Song (2):
  bpf: add rcu read_lock in bpf_get_current_[ancestor_]cgroup_id()
    helpers
  bpf: add missing bpf_read_[un]lock_trace() for syscall program

 kernel/bpf/helpers.c | 12 ++++++++++--
 net/bpf/test_run.c   |  4 ++++
 2 files changed, 14 insertions(+), 2 deletions(-)