On Sat, Jul 25, 2026 at 6:27 AM Leon Hwang <[email protected]> wrote: > > When CONFIG_FUNCTION_ERROR_INJECTION is disabled, a sleepable tracing prog > is allowed to attach to '__x64_'-alike prefix symbols. > > It is because the verifier does not verify whether the symbol is a kernel > function or a bpf prog. That said, a sleepable tracing prog is allowed to > attach to a bpf prog target whose name has '__x64_'-alike prefix. > > For example, a sleepable fentry prog attaches to a '__x64_sys_nop' XDP
we do have addr, so we should be able to distinguish between attaching to kernel function vs BPF program, no? > prog, and copies buffer from a user pointer with bpf_copy_from_user() > helper. After attaching the XDP prog to lo interface, the kernel BUG > could be triggered by 'ping -c 1 -W 1 127.0.0.1': > > [ 3.460756] BUG: sleeping function called from invalid context at > kernel/bpf/trampoline.c:1324 > > Fix it by disallowing sleepable tracing prog always when its target is > bpf prog. what happens when we freplace sleepable BPF program/subprogram with another sleepable BPF subprogram? And same question for sleepable fentry/fexit program attaching to sleepable BPF program? Is it something that just cannot work or we can actually allow that? > > Changes: > v1 -> v2: > * Drop redundant 'prog->sleepable' check. > * Collect Acked-by from Viktor, Thanks. > * v1: https://lore.kernel.org/bpf/[email protected]/ > > Leon Hwang (2): > bpf: Fix sleepable check for tracing prog > selftests/bpf: Verify rejection of sleepable tracing prog > > kernel/bpf/verifier.c | 9 ++- > .../selftests/bpf/prog_tests/fexit_bpf2bpf.c | 57 +++++++++++++++++++ > .../selftests/bpf/progs/fentry_sleepable.c | 19 +++++++ > tools/testing/selftests/bpf/progs/xdp_dummy.c | 6 ++ > 4 files changed, 88 insertions(+), 3 deletions(-) > create mode 100644 tools/testing/selftests/bpf/progs/fentry_sleepable.c > > -- > 2.55.0
