From 501b125a29f7cd8983960c5f3c80b337b1359cc3 Mon Sep 17 00:00:00 2001 From: Quentin Monnet Date: Wed, 29 May 2019 15:26:41 +0100 Subject: [PATCH] libbpf: prevent overwriting of log_level in bpf_object__load_progs() There are two functions in libbpf that support passing a log_level parameter for the verifier for loading programs: bpf_object__load_xattr() and bpf_prog_load_xattr(). Both accept an attribute object containing the log_level, and apply it to the programs to load. It turns out that to effectively load the programs, the latter function eventually relies on the former. This was not taken into account when adding support for log_level in bpf_object__load_xattr(), and the log_level passed to bpf_prog_load_xattr() later gets overwritten with a zero value, thus disabling verifier logs for the program in all cases: bpf_prog_load_xattr() // prog->log_level = attr1->log_level; -> bpf_object__load() // attr2->log_level = 0; -> bpf_object__load_xattr() // -> bpf_object__load_progs() // prog->log_level = attr2->log_level; Fix this by OR-ing the log_level in bpf_object__load_progs(), instead of overwriting it. v2: Fix commit log description (confusion on function names in v1). Fixes: 60276f984998 ("libbpf: add bpf_object__load_xattr() API function to pass log_level") Reported-by: Alexei Starovoitov Signed-off-by: Quentin Monnet Signed-off-by: Daniel Borkmann --- tools/lib/bpf/libbpf.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index ca4432f5b067..30cb08e2eb75 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -2232,7 +2232,7 @@ bpf_object__load_progs(struct bpf_object *obj, int log_level) for (i = 0; i < obj->nr_programs; i++) { if (bpf_program__is_function_storage(&obj->programs[i], obj)) continue; - obj->programs[i].log_level = log_level; + obj->programs[i].log_level |= log_level; err = bpf_program__load(&obj->programs[i], obj->license, obj->kern_version);