linux-kernel - [PATCH bpf v2] restore behaviour of CAP_SYS_ADMIN allowing the loading of networking bpf programs

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Message-Id: <20200620212616.93894-1-zenczykowski@gmail.com>
Date:   Sat, 20 Jun 2020 14:26:16 -0700
From:   Maciej Żenczykowski <zenczykowski@...il.com>
To:     Maciej Żenczykowski <maze@...gle.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>
Cc:     Linux Network Development Mailing List <netdev@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        BPF Mailing List <bpf@...r.kernel.org>,
        "David S . Miller" <davem@...emloft.net>,
        John Stultz <john.stultz@...aro.org>
Subject: [PATCH bpf v2] restore behaviour of CAP_SYS_ADMIN allowing the loading of networking bpf programs

From: Maciej Żenczykowski <maze@...gle.com>

This is a fix for a regression introduced in 5.8-rc1 by:
  commit 2c78ee898d8f10ae6fb2fa23a3fbaec96b1b7366
  'bpf: Implement CAP_BPF'

Before the above commit it was possible to load network bpf programs
with just the CAP_SYS_ADMIN privilege.

The Android bpfloader happens to run in such a configuration (it has
SYS_ADMIN but not NET_ADMIN) and creates maps and loads bpf programs
for later use by Android's netd (which has NET_ADMIN but not SYS_ADMIN).

Cc: Alexei Starovoitov <ast@...nel.org>
Cc: Daniel Borkmann <daniel@...earbox.net>
Reported-by: John Stultz <john.stultz@...aro.org>
Fixes: 2c78ee898d8f ("bpf: Implement CAP_BPF")
Signed-off-by: Maciej Żenczykowski <maze@...gle.com>
---
 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 8da159936bab..7d946435587d 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2121,7 +2121,7 @@ static int bpf_prog_load(union bpf_attr *attr, union bpf_attr __user *uattr)
 	    !bpf_capable())
 		return -EPERM;
 
-	if (is_net_admin_prog_type(type) && !capable(CAP_NET_ADMIN))
+	if (is_net_admin_prog_type(type) && !capable(CAP_NET_ADMIN) && !capable(CAP_SYS_ADMIN))
 		return -EPERM;
 	if (is_perfmon_prog_type(type) && !perfmon_capable())
 		return -EPERM;
-- 
2.27.0.111.gc72c7da667-goog