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@xxxxxxxxxx/ [2] https://lore.kernel.org/bpf/20210728172307.1030271-1-yhs@xxxxxx/ 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(-) -- 2.30.2
