[PATCH net-next 1/2] bpf: Allow CGROUP_SKB eBPF program to access sk_buff

[PATCH net-next 1/2] bpf: Allow CGROUP_SKB eBPF program to access sk_buff

[Chenbo Feng]

From: Chenbo Feng <fengc@google.com>

This allows cgroup eBPF program to classify packet based on their
protocol or other detail information. Currently program need
CAP_NET_ADMIN privilege to attach a cgroup eBPF program, and A
process with CAP_NET_ADMIN can already see all packets on the system,
for example, by creating an iptables rules that causes the packet to
be passed to userspace via NFLOG.

Signed-off-by: Chenbo Feng <fengc@google.com>
---
 kernel/bpf/verifier.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 339c8a1..94a9bc9 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2419,6 +2419,7 @@ static bool may_access_skb(enum bpf_prog_type type)
 	case BPF_PROG_TYPE_SOCKET_FILTER:
 	case BPF_PROG_TYPE_SCHED_CLS:
 	case BPF_PROG_TYPE_SCHED_ACT:
+	case BPF_PROG_TYPE_CGROUP_SKB:
 		return true;
 	default:
 		return false;
-- 
2.7.4

[PATCH net-next 2/2] bpf: Remove the capability check for cgroup skb eBPF program

[Chenbo Feng]

From: Chenbo Feng <fengc@google.com>

Currently loading a cgroup skb eBPF program require a CAP_SYS_ADMIN
capability while attaching the program to a cgroup only requires the
user have CAP_NET_ADMIN privilege. We can escape the capability
check when load the program just like socket filter program to make
the capability requirement consistent.

Signed-off-by: Chenbo Feng <fengc@google.com>
---
 kernel/bpf/syscall.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 265a0d8..021c0b4 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -815,7 +815,9 @@ static int bpf_prog_load(union bpf_attr *attr)
 	    attr->kern_version != LINUX_VERSION_CODE)
 		return -EINVAL;
 
-	if (type != BPF_PROG_TYPE_SOCKET_FILTER && !capable(CAP_SYS_ADMIN))
+	if (type != BPF_PROG_TYPE_SOCKET_FILTER
+	    && type != BPF_PROG_TYPE_CGROUP_SKB
+	    && !capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
 	/* plain bpf_prog allocation */
-- 
2.7.4

RE: [PATCH net-next 2/2] bpf: Remove the capability check for cgroup skb eBPF program

[YUAN Linyu]

hi

> -----Original Message-----
> From: netdev-owner@vger.kernel.org [mailto:netdev-owner@vger.kernel.org]
> On Behalf Of Chenbo Feng
> Sent: Thursday, June 01, 2017 2:07 AM
> To: netdev@vger.kernel.org; David Miller
> Cc: Lorenzo Colitti; Chenbo Feng
> Subject: [PATCH net-next 2/2] bpf: Remove the capability check for cgroup skb
> eBPF program
> -	if (type != BPF_PROG_TYPE_SOCKET_FILTER
> && !capable(CAP_SYS_ADMIN))
> +	if (type != BPF_PROG_TYPE_SOCKET_FILTER
> +	    && type != BPF_PROG_TYPE_CGROUP_SKB
> +	    && !capable(CAP_SYS_ADMIN))

checkpatch.pl prefer put && at end of line

>  		return -EPERM;
> 
>  	/* plain bpf_prog allocation */
> --
> 2.7.4