[PATCH net-next 2/3 v2] bpf: change helper bpf_probe_read arg2 type to ARG_CONST_SIZE_OR_ZERO
From: Yonghong Song <hidden>
Date: 2017-11-12 16:04:03
Subsystem:
bpf [general] (safe dynamic programs and tools), bpf [security & lsm] (security audit and enforcement using bpf), bpf [tracing], the rest, tracing · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, KP Singh, Matt Bobrowski, Song Liu, Linus Torvalds, Steven Rostedt, Masami Hiramatsu
The helper bpf_probe_read arg2 type is changed from ARG_CONST_SIZE to ARG_CONST_SIZE_OR_ZERO to permit size-0 buffer. Together with newer ARG_CONST_SIZE_OR_ZERO semantics which allows non-NULL buffer with size 0, this allows simpler bpf programs with verifier acceptance. The previous commit which changes ARG_CONST_SIZE_OR_ZERO semantics has details on examples. Signed-off-by: Yonghong Song <redacted> Acked-by: Alexei Starovoitov <ast@kernel.org> --- kernel/trace/bpf_trace.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 506efe6..a5580c6 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c@@ -78,12 +78,16 @@ EXPORT_SYMBOL_GPL(trace_call_bpf); BPF_CALL_3(bpf_probe_read, void *, dst, u32, size, const void *, unsafe_ptr) { - int ret; + int ret = 0; + + if (unlikely(size == 0)) + goto out; ret = probe_kernel_read(dst, unsafe_ptr, size); if (unlikely(ret < 0)) memset(dst, 0, size); + out: return ret; }
@@ -92,7 +96,7 @@ static const struct bpf_func_proto bpf_probe_read_proto = { .gpl_only = true, .ret_type = RET_INTEGER, .arg1_type = ARG_PTR_TO_UNINIT_MEM, - .arg2_type = ARG_CONST_SIZE, + .arg2_type = ARG_CONST_SIZE_OR_ZERO, .arg3_type = ARG_ANYTHING, };
--
2.9.5