linux-kernel - [PATCH 5.19 014/155] bpf: Restrict bpf_sys_bpf to CAP

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Message-Id: <20220906132830.033423812@linuxfoundation.org>
Date:   Tue,  6 Sep 2022 15:29:22 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, YiFei Zhu <zhuyifei@...gle.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.19 014/155] bpf: Restrict bpf_sys_bpf to CAP_PERFMON

From: YiFei Zhu <zhuyifei@...gle.com>

[ Upstream commit 14b20b784f59bdd95f6f1cfb112c9818bcec4d84 ]

The verifier cannot perform sufficient validation of any pointers passed
into bpf_attr and treats them as integers rather than pointers. The helper
will then read from arbitrary pointers passed into it. Restrict the helper
to CAP_PERFMON since the security model in BPF of arbitrary kernel read is
CAP_BPF + CAP_PERFMON.

Fixes: af2ac3e13e45 ("bpf: Prepare bpf syscall to be used from kernel and user space.")
Signed-off-by: YiFei Zhu <zhuyifei@...gle.com>
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Acked-by: Alexei Starovoitov <ast@...nel.org>
Link: https://lore.kernel.org/bpf/20220816205517.682470-1-zhuyifei@google.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 kernel/bpf/syscall.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 82e83cfb4114a..dd0fc2a86ce17 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -5153,7 +5153,7 @@ syscall_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 {
 	switch (func_id) {
 	case BPF_FUNC_sys_bpf:
-		return &bpf_sys_bpf_proto;
+		return !perfmon_capable() ? NULL : &bpf_sys_bpf_proto;
 	case BPF_FUNC_btf_find_by_name_kind:
 		return &bpf_btf_find_by_name_kind_proto;
 	case BPF_FUNC_sys_close:
-- 
2.35.1