mbox series

[bpf,v2,0/2] bpf: fix a couple of issues with syscall program

Message ID 20210809060310.1174777-1-yhs@fb.com (mailing list archive)
Headers show
Series bpf: fix a couple of issues with syscall program | expand

Message

Yonghong Song Aug. 9, 2021, 6:03 a.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.

Previous version ([2]) tried to add rcu_read_lock() surrounding
bpf_prog_run_pin_on_cpu() for syscall program. This doesn't work
and will trigger other warning since syscall program is a sleepable
program.

In this version, patch #1 disallows to call
bpf_get_current_cgroup_id() and bpf_get_current_ancestor_cgroup_id()
for sleepable programs to silence the warning. Further, syscall program
should be protected with bpf_read_lock_trace() which is implemented
in Patch #2.

 [1] https://lore.kernel.org/bpf/0000000000006d5cab05c7d9bb87@google.com/
 [2] https://lore.kernel.org/bpf/20210728172307.1030271-1-yhs@fb.com/

Changelog:
  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: don't call bpf_get_current_[ancestor_]cgroup_id() in sleepable
    progs
  bpf: add missing bpf_read_[un]lock_trace() for syscall program

 kernel/trace/bpf_trace.c | 6 ++++--
 net/bpf/test_run.c       | 4 ++++
 2 files changed, 8 insertions(+), 2 deletions(-)