From 584b2c7ce24450a7c687f976b54333607e14e058 Mon Sep 17 00:00:00 2001 From: Jiri Olsa Date: Wed, 5 May 2021 15:25:29 +0200 Subject: [PATCH] bpf: Forbid trampoline attach for functions with variable arguments [ Upstream commit 31379397dcc364a59ce764fabb131b645c43e340 ] We can't currently allow to attach functions with variable arguments. The problem is that we should save all the registers for arguments, which is probably doable, but if caller uses more than 6 arguments, we need stack data, which will be wrong, because of the extra stack frame we do in bpf trampoline, so we could crash. Also currently there's malformed trampoline code generated for such functions at the moment as described in: https://lore.kernel.org/bpf/20210429212834.82621-1-jolsa@kernel.org/ Signed-off-by: Jiri Olsa Signed-off-by: Daniel Borkmann Acked-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20210505132529.401047-1-jolsa@kernel.org Signed-off-by: Sasha Levin --- kernel/bpf/btf.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index ed7d02e8bc939..aaf2fbaa0cc76 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -4960,6 +4960,12 @@ int btf_distill_func_proto(struct bpf_verifier_log *log, m->ret_size = ret; for (i = 0; i < nargs; i++) { + if (i == nargs - 1 && args[i].type == 0) { + bpf_log(log, + "The function %s with variable args is unsupported.\n", + tname); + return -EINVAL; + } ret = __get_type_size(btf, args[i].type, &t); if (ret < 0) { bpf_log(log, @@ -4967,6 +4973,12 @@ int btf_distill_func_proto(struct bpf_verifier_log *log, tname, i, btf_kind_str[BTF_INFO_KIND(t->info)]); return -EINVAL; } + if (ret == 0) { + bpf_log(log, + "The function %s has malformed void argument.\n", + tname); + return -EINVAL; + } m->arg_size[i] = ret; } m->nr_args = nargs;