Commit ebc614f6 authored by Roman Gushchin's avatar Roman Gushchin Committed by David S. Miller
Browse files

bpf, cgroup: implement eBPF-based device controller for cgroup v2 



Cgroup v2 lacks the device controller, provided by cgroup v1.
This patch adds a new eBPF program type, which in combination
of previously added ability to attach multiple eBPF programs
to a cgroup, will provide a similar functionality, but with some
additional flexibility.

This patch introduces a BPF_PROG_TYPE_CGROUP_DEVICE program type.
A program takes major and minor device numbers, device type
(block/character) and access type (mknod/read/write) as parameters
and returns an integer which defines if the operation should be
allowed or terminated with -EPERM.

Signed-off-by: default avatarRoman Gushchin <guro@fb.com>
Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent ecf8fecb

include/linux/bpf-cgroup.h

+15 −0
Original line number Diff line number Diff line
@@ -67,6 +67,9 @@ int __cgroup_bpf_run_filter_sock_ops(struct sock *sk, 
				     struct bpf_sock_ops_kern *sock_ops,

				     enum bpf_attach_type type);



int __cgroup_bpf_check_dev_permission(short dev_type, u32 major, u32 minor,

				      short access, enum bpf_attach_type type);



/* Wrappers for __cgroup_bpf_run_filter_skb() guarded by cgroup_bpf_enabled. */

#define BPF_CGROUP_RUN_PROG_INET_INGRESS(sk, skb)			      \

({									      \
@@ -112,6 +115,17 @@ int __cgroup_bpf_run_filter_sock_ops(struct sock *sk, 
	}								       \

	__ret;								       \

})



#define BPF_CGROUP_RUN_PROG_DEVICE_CGROUP(type, major, minor, access)	      \

({									      \

	int __ret = 0;							      \

	if (cgroup_bpf_enabled)						      \

		__ret = __cgroup_bpf_check_dev_permission(type, major, minor, \

							  access,	      \

							  BPF_CGROUP_DEVICE); \

									      \

	__ret;								      \

})

#else



struct cgroup_bpf {};
@@ -122,6 +136,7 @@ static inline int cgroup_bpf_inherit(struct cgroup *cgrp) { return 0; } 
#define BPF_CGROUP_RUN_PROG_INET_EGRESS(sk,skb) ({ 0; })

#define BPF_CGROUP_RUN_PROG_INET_SOCK(sk) ({ 0; })

#define BPF_CGROUP_RUN_PROG_SOCK_OPS(sock_ops) ({ 0; })

#define BPF_CGROUP_RUN_PROG_DEVICE_CGROUP(type,major,minor,access) ({ 0; })



#endif /* CONFIG_CGROUP_BPF */

include/linux/bpf_types.h

+3 −0
Original line number Diff line number Diff line
@@ -19,6 +19,9 @@ BPF_PROG_TYPE(BPF_PROG_TYPE_KPROBE, kprobe) 
BPF_PROG_TYPE(BPF_PROG_TYPE_TRACEPOINT, tracepoint)

BPF_PROG_TYPE(BPF_PROG_TYPE_PERF_EVENT, perf_event)

#endif

#ifdef CONFIG_CGROUP_BPF

BPF_PROG_TYPE(BPF_PROG_TYPE_CGROUP_DEVICE, cg_dev)

#endif



BPF_MAP_TYPE(BPF_MAP_TYPE_ARRAY, array_map_ops)

BPF_MAP_TYPE(BPF_MAP_TYPE_PERCPU_ARRAY, percpu_array_map_ops)

include/linux/device_cgroup.h

+7 −1
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: GPL-2.0 */

#include <linux/fs.h>

#include <linux/bpf-cgroup.h>



#define DEVCG_ACC_MKNOD 1

#define DEVCG_ACC_READ  2
@@ -19,10 +20,15 @@ static inline int __devcgroup_check_permission(short type, u32 major, u32 minor, 
{ return 0; }

#endif



#ifdef CONFIG_CGROUP_DEVICE

#if defined(CONFIG_CGROUP_DEVICE) || defined(CONFIG_CGROUP_BPF)

static inline int devcgroup_check_permission(short type, u32 major, u32 minor,

					     short access)

{

	int rc = BPF_CGROUP_RUN_PROG_DEVICE_CGROUP(type, major, minor, access);



	if (rc)

		return -EPERM;



	return __devcgroup_check_permission(type, major, minor, access);

}

include/uapi/linux/bpf.h

+15 −0
Original line number Diff line number Diff line
@@ -132,6 +132,7 @@ enum bpf_prog_type { 
	BPF_PROG_TYPE_LWT_XMIT,

	BPF_PROG_TYPE_SOCK_OPS,

	BPF_PROG_TYPE_SK_SKB,

	BPF_PROG_TYPE_CGROUP_DEVICE,

};



enum bpf_attach_type {
@@ -141,6 +142,7 @@ enum bpf_attach_type { 
	BPF_CGROUP_SOCK_OPS,

	BPF_SK_SKB_STREAM_PARSER,

	BPF_SK_SKB_STREAM_VERDICT,

	BPF_CGROUP_DEVICE,

	__MAX_BPF_ATTACH_TYPE

};
@@ -991,4 +993,17 @@ struct bpf_perf_event_value { 
	__u64 running;

};



#define BPF_DEVCG_ACC_MKNOD	(1ULL << 0)

#define BPF_DEVCG_ACC_READ	(1ULL << 1)

#define BPF_DEVCG_ACC_WRITE	(1ULL << 2)



#define BPF_DEVCG_DEV_BLOCK	(1ULL << 0)

#define BPF_DEVCG_DEV_CHAR	(1ULL << 1)



struct bpf_cgroup_dev_ctx {

	__u32 access_type; /* (access << 16) | type */

	__u32 major;

	__u32 minor;

};



#endif /* _UAPI__LINUX_BPF_H__ */

kernel/bpf/cgroup.c

+67 −0
Original line number Diff line number Diff line
@@ -522,3 +522,70 @@ int __cgroup_bpf_run_filter_sock_ops(struct sock *sk, 
	return ret == 1 ? 0 : -EPERM;

}

EXPORT_SYMBOL(__cgroup_bpf_run_filter_sock_ops);



int __cgroup_bpf_check_dev_permission(short dev_type, u32 major, u32 minor,

				      short access, enum bpf_attach_type type)

{

	struct cgroup *cgrp;

	struct bpf_cgroup_dev_ctx ctx = {

		.access_type = (access << 16) | dev_type,

		.major = major,

		.minor = minor,

	};

	int allow = 1;



	rcu_read_lock();

	cgrp = task_dfl_cgroup(current);

	allow = BPF_PROG_RUN_ARRAY(cgrp->bpf.effective[type], &ctx,

				   BPF_PROG_RUN);

	rcu_read_unlock();



	return !allow;

}

EXPORT_SYMBOL(__cgroup_bpf_check_dev_permission);



static const struct bpf_func_proto *

cgroup_dev_func_proto(enum bpf_func_id func_id)

{

	switch (func_id) {

	case BPF_FUNC_map_lookup_elem:

		return &bpf_map_lookup_elem_proto;

	case BPF_FUNC_map_update_elem:

		return &bpf_map_update_elem_proto;

	case BPF_FUNC_map_delete_elem:

		return &bpf_map_delete_elem_proto;

	case BPF_FUNC_get_current_uid_gid:

		return &bpf_get_current_uid_gid_proto;

	case BPF_FUNC_trace_printk:

		if (capable(CAP_SYS_ADMIN))

			return bpf_get_trace_printk_proto();

	default:

		return NULL;

	}

}



static bool cgroup_dev_is_valid_access(int off, int size,

				       enum bpf_access_type type,

				       struct bpf_insn_access_aux *info)

{

	if (type == BPF_WRITE)

		return false;



	if (off < 0 || off + size > sizeof(struct bpf_cgroup_dev_ctx))

		return false;

	/* The verifier guarantees that size > 0. */

	if (off % size != 0)

		return false;

	if (size != sizeof(__u32))

		return false;



	return true;

}



const struct bpf_prog_ops cg_dev_prog_ops = {

};



const struct bpf_verifier_ops cg_dev_verifier_ops = {

	.get_func_proto		= cgroup_dev_func_proto,

	.is_valid_access	= cgroup_dev_is_valid_access,

};

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