current/SOURCES/bpf-restrict-bpf_sys_bpf-to-cap_perfmon.patch

From 702b62a2eead72e41d0ea01a15165d756708d4cf Mon Sep 17 00:00:00 2001
From: Sasha Levin <sashal@kernel.org>
Date: Tue, 16 Aug 2022 20:55:16 +0000
Subject: bpf: Restrict bpf_sys_bpf to CAP_PERFMON

From: YiFei Zhu <zhuyifei@google.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@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220816205517.682470-1-zhuyifei@google.com
Signed-off-by: Sasha Levin <sashal@kernel.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

1	From 702b62a2eead72e41d0ea01a15165d756708d4cf Mon Sep 17 00:00:00 2001
2	From: Sasha Levin <sashal@kernel.org>
3	Date: Tue, 16 Aug 2022 20:55:16 +0000
4	Subject: bpf: Restrict bpf_sys_bpf to CAP_PERFMON
5
6	From: YiFei Zhu <zhuyifei@google.com>
7
8	[ Upstream commit 14b20b784f59bdd95f6f1cfb112c9818bcec4d84 ]
9
10	The verifier cannot perform sufficient validation of any pointers passed
11	into bpf_attr and treats them as integers rather than pointers. The helper
12	will then read from arbitrary pointers passed into it. Restrict the helper
13	to CAP_PERFMON since the security model in BPF of arbitrary kernel read is
14	CAP_BPF + CAP_PERFMON.
15
16	Fixes: af2ac3e13e45 ("bpf: Prepare bpf syscall to be used from kernel and user space.")
17	Signed-off-by: YiFei Zhu <zhuyifei@google.com>
18	Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
19	Acked-by: Alexei Starovoitov <ast@kernel.org>
20	Link: https://lore.kernel.org/bpf/20220816205517.682470-1-zhuyifei@google.com
21	Signed-off-by: Sasha Levin <sashal@kernel.org>
22	---
23	kernel/bpf/syscall.c \| 2 +-
24	1 file changed, 1 insertion(+), 1 deletion(-)
25
26	diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
27	index 82e83cfb4114a..dd0fc2a86ce17 100644
28	--- a/kernel/bpf/syscall.c
29	+++ b/kernel/bpf/syscall.c
30	@@ -5153,7 +5153,7 @@ syscall_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
31	{
32	switch (func_id) {
33	case BPF_FUNC_sys_bpf:
34	- return &bpf_sys_bpf_proto;
35	+ return !perfmon_capable() ? NULL : &bpf_sys_bpf_proto;
36	case BPF_FUNC_btf_find_by_name_kind:
37	return &bpf_btf_find_by_name_kind_proto;
38	case BPF_FUNC_sys_close:
39	--
40	2.35.1
41