netdev - [PATCH bpf] bpf_trace: bail out from bpf_kprobe_multi_link

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Message-ID: <20220506142148.GA24802@asgard.redhat.com>
Date:   Fri, 6 May 2022 16:21:48 +0200
From:   Eugene Syromiatnikov <esyr@...hat.com>
To:     Jiri Olsa <jolsa@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH bpf] bpf_trace: bail out from bpf_kprobe_multi_link_attach
 when in compat

Since bpf_kprobe_multi_link_attach doesn't support 32-bit kernels
for whatever reason, having it enabled for compat processes on 64-bit
kernels makes even less sense due to discrepances in the type sizes
that it does not handle.

Fixes: 0dcac272540613d4 ("bpf: Add multi kprobe link")
Signed-off-by: Eugene Syromiatnikov <esyr@...hat.com>
---
 kernel/trace/bpf_trace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index d8553f4..9560af6 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -2410,7 +2410,7 @@ int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr
 	int err;
 
 	/* no support for 32bit archs yet */
-	if (sizeof(u64) != sizeof(void *))
+	if (sizeof(u64) != sizeof(void *) || in_compat_syscall())
 		return -EOPNOTSUPP;
 
 	if (prog->expected_attach_type != BPF_TRACE_KPROBE_MULTI)
-- 
2.1.4