From eb33f2cca49ec49a1b893b5af546e7c042ca6365 Mon Sep 17 00:00:00 2001 From: Gianluca Borello Date: Wed, 22 Nov 2017 18:32:54 +0000 Subject: [PATCH] bpf: remove explicit handling of 0 for arg2 in bpf_probe_read Commit 9c019e2bc4b2 ("bpf: change helper bpf_probe_read arg2 type to ARG_CONST_SIZE_OR_ZERO") changed arg2 type to ARG_CONST_SIZE_OR_ZERO to simplify writing bpf programs by taking advantage of the new semantics introduced for ARG_CONST_SIZE_OR_ZERO which allows arguments. In order to prevent the helper from actually passing a NULL pointer to probe_kernel_read, which can happen when is passed to the helper, the commit also introduced an explicit check against size == 0. After the recent introduction of the ARG_PTR_TO_MEM_OR_NULL type, bpf_probe_read can not receive a pair of arguments anymore, thus the check is not needed anymore and can be removed, since probe_kernel_read can correctly handle a call. This also fixes the semantics of the helper before it gets officially released and bpf programs start relying on this check. Fixes: 9c019e2bc4b2 ("bpf: change helper bpf_probe_read arg2 type to ARG_CONST_SIZE_OR_ZERO") Signed-off-by: Gianluca Borello Acked-by: Alexei Starovoitov Acked-by: Daniel Borkmann Acked-by: Yonghong Song Signed-off-by: Daniel Borkmann --- kernel/trace/bpf_trace.c | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-) diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index a5580c6708668..728909f7951ca 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -78,16 +78,12 @@ EXPORT_SYMBOL_GPL(trace_call_bpf); BPF_CALL_3(bpf_probe_read, void *, dst, u32, size, const void *, unsafe_ptr) { - int ret = 0; - - if (unlikely(size == 0)) - goto out; + int ret; ret = probe_kernel_read(dst, unsafe_ptr, size); if (unlikely(ret < 0)) memset(dst, 0, size); - out: return ret; } -- 2.39.5