Re: [PATCH bpf-next v3 1/2] bpf: support bpf_get_func_arg() for BPF_TRACE_RAW_TP
flat view
From: bot+bpf-ci@kernel.org
Date: 2026-01-19 18:44:53
Also in:
bpf, lkml
quoted hunk ↗ jump to hunk
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index f73e08c223b5..64976009ba3c 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c@@ -1734,11 +1734,11 @@ tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) case BPF_FUNC_d_path: return &bpf_d_path_proto; case BPF_FUNC_get_func_arg: - return bpf_prog_has_trampoline(prog) ? &bpf_get_func_arg_proto : NULL; + return &bpf_get_func_arg_proto;
Removing the bpf_prog_has_trampoline() check here allows all TRACING
program types to use bpf_get_func_arg(), not just RAW_TP and trampoline-
based types. In particular, BPF_TRACE_ITER programs can now use this
helper.
However, looking at do_misc_fixups() in verifier.c, the inline code
generation only handles BPF_TRACE_RAW_TP specially. For other non-
trampoline types like BPF_TRACE_ITER, the else branch generates:
BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_1, -8)
This loads nr_args from ctx-8, but ITER programs use a different context
layout (e.g. struct bpf_iter__bpf_map_elem with meta, map, key, value
pointers). There is no nr_args at ctx-8 for ITER programs.
Would this cause ITER programs using bpf_get_func_arg() to read arbitrary
memory at ctx-8, potentially leaking kernel data or causing incorrect
bounds checks for subsequent argument access?
quoted hunk ↗ jump to hunk
case BPF_FUNC_get_func_ret: return bpf_prog_has_trampoline(prog) ? &bpf_get_func_ret_proto : NULL; case BPF_FUNC_get_func_arg_cnt: - return bpf_prog_has_trampoline(prog) ? &bpf_get_func_arg_cnt_proto : NULL; + return &bpf_get_func_arg_cnt_proto;
Same question applies here for bpf_get_func_arg_cnt() with ITER programs.
quoted hunk ↗ jump to hunk
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 9de0ec0c3ed9..0b281b7c41eb 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c@@ -23323,8 +23323,20 @@ static int do_misc_fixups(struct bpf_verifier_env *env) /* Implement bpf_get_func_arg inline. */ if (prog_type == BPF_PROG_TYPE_TRACING && insn->imm == BPF_FUNC_get_func_arg) { + if (eatype == BPF_TRACE_RAW_TP) { + int nr_args = btf_type_vlen(prog->aux->attach_func_proto); + + /* + * skip first 'void *__data' argument in btf_trace_##name + * typedef + */ + nr_args--; + /* Save nr_args to reg0 */ + insn_buf[0] = BPF_MOV64_IMM(BPF_REG_0, nr_args); + } else { + /* Load nr_args from ctx - 8 */ + insn_buf[0] = BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_1, -8); + }
This else branch now applies to BPF_TRACE_ITER as well, since the trampoline check was removed in tracing_prog_func_proto(). Should the condition be extended to also handle ITER, or should ITER be explicitly blocked from using these helpers? [ ... ] --- AI reviewed your patch. Please fix the bug or email reply why it's not a bug. See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md CI run summary: https://github.com/kernel-patches/bpf/actions/runs/21147849826