libbpf: Fix potential uninit memory read

In case of BPF_CORE_TYPE_ID_LOCAL we fill out target result explicitly.
But targ_res itself isn't initialized in such a case, and subsequent
call to bpf_core_patch_insn() might read uninitialized field (like
fail_memsz_adjust in this case). So ensure that targ_res is
zero-initialized for BPF_CORE_TYPE_ID_LOCAL case.

This was reported by Coverity static analyzer.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211214010032.3843804-1-andrii@kernel.org

diff --git a/tools/lib/bpf/relo_core.c b/tools/lib/bpf/relo_core.c
index c770483..910865e 100644 (file)
--- a/tools/lib/bpf/relo_core.c
+++ b/tools/lib/bpf/relo_core.c
@@ -1223,6 +1223,7 @@ int bpf_core_apply_relo_insn(const char *prog_name, struct bpf_insn *insn,
        /* TYPE_ID_LOCAL relo is special and doesn't need candidate search */
        if (relo->kind == BPF_CORE_TYPE_ID_LOCAL) {
                /* bpf_insn's imm value could get out of sync during linking */
+               memset(&targ_res, 0, sizeof(targ_res));
                targ_res.validate = false;
                targ_res.poison = false;
                targ_res.orig_val = local_spec->root_type_id;