[PATCH AUTOSEL 5.5 020/121] libbpf: Ignore incompatible types with matching name during CO-RE relocation

Sasha Levin
2020-04-11T23:40:00Z

From: Andrii Nakryiko <andriin@fb.com>

[ Upstream commit d121e1d34b72c4975ff0340901d926c0aaf98174 ]

When finding target type candidates, ignore forward declarations, functions,
and other named types of incompatible kind. Not doing this can cause false
errors. See [0] for one such case (due to struct pt_regs forward
declaration).

[0] https://github.com/iovisor/bcc/pull/2806#issuecomment-598543645

Fixes: ddc7c3042614 ("libbpf: implement BPF CO-RE offset relocation algorithm")
Reported-by: Wenbo Zhang <ethercflow@gmail.com>
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20200313172336.1879637-3-andriin@fb.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
tools/lib/bpf/libbpf.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 6d1bb761a544c..cff248e1f1434 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -2737,6 +2737,10 @@ static struct ids_vec *bpf_core_find_cands(const struct btf *local_btf,
if (str_is_empty(targ_name))
continue;

+ t = skip_mods_and_typedefs(targ_btf, i, NULL);
+ if (!btf_is_composite(t) && !btf_is_array(t))
+ continue;
+
targ_essent_len = bpf_core_essential_name_len(targ_name);
if (targ_essent_len != local_essent_len)
continue;
--
2.20.1