Message ID | 20171112000036.3597189-3-yhs@fb.com |
---|---|
State | Accepted, archived |
Delegated to: | David Miller |
Headers | show |
Series | bpf: improve verifier ARG_CONST_SIZE_OR_ZERO semantics | expand |
Hello! On 11/12/2017 3:00 AM, Yonghong Song wrote: > 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 prvious commit which changes ARG_CONST_SIZE_OR_ZERO semantics Previous. > has details on examples. > > Signed-off-by: Yonghong Song <yhs@fb.com> > Acked-by: Alexei Starovoitov <ast@kernel.org> [...] MBR, Sergei
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, };