From: KP Singh <kpsingh@google.com>
Date: Wed, 23 Oct 2019 17:40:38 +0200
Subject: libbpf: Fix strncat bounds error in libbpf_prog_type_by_name
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Patch-mainline: Queued in subsystem maintainer repository
Git-repo: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Git-commit: 58eeb2289ab9bd8acad41a589431bbdbf7622595
References: bsc#1155518

On compiling samples with this change, one gets an error:

 error: ‘strncat’ specified bound 118 equals destination size
  [-Werror=stringop-truncation]

    strncat(dst, name + section_names[i].len,
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     sizeof(raw_tp_btf_name) - (dst - raw_tp_btf_name));
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

strncat requires the destination to have enough space for the
terminating null byte.

Fixes: f75a697e09137 ("libbpf: Auto-detect btf_id of BTF-based raw_tracepoint")
Signed-off-by: KP Singh <kpsingh@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20191023154038.24075-1-kpsingh@chromium.org
Acked-by: Gary Lin <glin@suse.com>
---
 tools/lib/bpf/libbpf.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -4608,7 +4608,7 @@ int libbpf_prog_type_by_name(const char
 			}
 			/* prepend "btf_trace_" prefix per kernel convention */
 			strncat(dst, name + section_names[i].len,
-				sizeof(raw_tp_btf_name) - (dst - raw_tp_btf_name));
+				sizeof(raw_tp_btf_name) - sizeof("btf_trace_"));
 			ret = btf__find_by_name(btf, raw_tp_btf_name);
 			btf__free(btf);
 			if (ret <= 0) {