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Message-ID: <20180217073617.GA8226@ircssh-2.c.rugged-nimbus-611.internal>
Date: Sat, 17 Feb 2018 07:36:20 +0000
From: Sargun Dhillon <sargun@...gun.me>
To: netdev@...r.kernel.org, containers@...ts.linux-foundation.org
Cc: ast@...nel.org, daniel@...earbox.net, keescook@...omium.org,
luto@...capital.net, wad@...omium.org, me@...sfraz.com,
cpuguy83@...il.com, tom.hromatka@...cle.com
Subject: [net-next v2 2/2] bpf: Add eBPF seccomp sample programs
This adds a sample program that uses seccomp-eBPF, called
seccomp1. It shows the simple ability to code seccomp filters
in C.
Signed-off-by: Sargun Dhillon <sargun@...gun.me>
---
samples/bpf/Makefile | 5 +++++
samples/bpf/bpf_load.c | 9 +++++++--
samples/bpf/seccomp1_kern.c | 43 +++++++++++++++++++++++++++++++++++++++++++
samples/bpf/seccomp1_user.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 100 insertions(+), 2 deletions(-)
create mode 100644 samples/bpf/seccomp1_kern.c
create mode 100644 samples/bpf/seccomp1_user.c
diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index ec3fc8d88e87..264838846f71 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -43,6 +43,7 @@ hostprogs-y += xdp_redirect_cpu
hostprogs-y += xdp_monitor
hostprogs-y += xdp_rxq_info
hostprogs-y += syscall_tp
+hostprogs-y += seccomp1
# Libbpf dependencies
LIBBPF := ../../tools/lib/bpf/bpf.o ../../tools/lib/bpf/nlattr.o
@@ -93,6 +94,8 @@ xdp_redirect_cpu-objs := bpf_load.o $(LIBBPF) xdp_redirect_cpu_user.o
xdp_monitor-objs := bpf_load.o $(LIBBPF) xdp_monitor_user.o
xdp_rxq_info-objs := bpf_load.o $(LIBBPF) xdp_rxq_info_user.o
syscall_tp-objs := bpf_load.o $(LIBBPF) syscall_tp_user.o
+seccomp1-objs := bpf_load.o $(LIBBPF) seccomp1_user.o
+
# Tell kbuild to always build the programs
always := $(hostprogs-y)
@@ -144,6 +147,7 @@ always += xdp_monitor_kern.o
always += xdp_rxq_info_kern.o
always += xdp2skb_meta_kern.o
always += syscall_tp_kern.o
+always += seccomp1_kern.o
HOSTCFLAGS += -I$(objtree)/usr/include
HOSTCFLAGS += -I$(srctree)/tools/lib/
@@ -188,6 +192,7 @@ HOSTLOADLIBES_xdp_redirect_cpu += -lelf
HOSTLOADLIBES_xdp_monitor += -lelf
HOSTLOADLIBES_xdp_rxq_info += -lelf
HOSTLOADLIBES_syscall_tp += -lelf
+HOSTLOADLIBES_seccomp1 += -lelf
# Allows pointing LLC/CLANG to a LLVM backend with bpf support, redefine on cmdline:
# make samples/bpf/ LLC=~/git/llvm/build/bin/llc CLANG=~/git/llvm/build/bin/clang
diff --git a/samples/bpf/bpf_load.c b/samples/bpf/bpf_load.c
index 69806d74fa53..856bc8b93916 100644
--- a/samples/bpf/bpf_load.c
+++ b/samples/bpf/bpf_load.c
@@ -67,6 +67,7 @@ static int load_and_attach(const char *event, struct bpf_insn *prog, int size)
bool is_cgroup_sk = strncmp(event, "cgroup/sock", 11) == 0;
bool is_sockops = strncmp(event, "sockops", 7) == 0;
bool is_sk_skb = strncmp(event, "sk_skb", 6) == 0;
+ bool is_seccomp = strncmp(event, "seccomp", 7) == 0;
size_t insns_cnt = size / sizeof(struct bpf_insn);
enum bpf_prog_type prog_type;
char buf[256];
@@ -96,6 +97,8 @@ static int load_and_attach(const char *event, struct bpf_insn *prog, int size)
prog_type = BPF_PROG_TYPE_SOCK_OPS;
} else if (is_sk_skb) {
prog_type = BPF_PROG_TYPE_SK_SKB;
+ } else if (is_seccomp) {
+ prog_type = BPF_PROG_TYPE_SECCOMP;
} else {
printf("Unknown event '%s'\n", event);
return -1;
@@ -110,7 +113,8 @@ static int load_and_attach(const char *event, struct bpf_insn *prog, int size)
prog_fd[prog_cnt++] = fd;
- if (is_xdp || is_perf_event || is_cgroup_skb || is_cgroup_sk)
+ if (is_xdp || is_perf_event || is_cgroup_skb || is_cgroup_sk ||
+ is_seccomp)
return 0;
if (is_socket || is_sockops || is_sk_skb) {
@@ -589,7 +593,8 @@ static int do_load_bpf_file(const char *path, fixup_map_cb fixup_map)
memcmp(shname, "socket", 6) == 0 ||
memcmp(shname, "cgroup/", 7) == 0 ||
memcmp(shname, "sockops", 7) == 0 ||
- memcmp(shname, "sk_skb", 6) == 0) {
+ memcmp(shname, "sk_skb", 6) == 0 ||
+ memcmp(shname, "seccomp", 7) == 0) {
ret = load_and_attach(shname, data->d_buf,
data->d_size);
if (ret != 0)
diff --git a/samples/bpf/seccomp1_kern.c b/samples/bpf/seccomp1_kern.c
new file mode 100644
index 000000000000..420e37eebd92
--- /dev/null
+++ b/samples/bpf/seccomp1_kern.c
@@ -0,0 +1,43 @@
+#include <uapi/linux/seccomp.h>
+#include <uapi/linux/bpf.h>
+#include <uapi/linux/unistd.h>
+#include "bpf_helpers.h"
+#include <uapi/linux/errno.h>
+#include <uapi/linux/audit.h>
+
+#if defined(__x86_64__)
+#define ARCH AUDIT_ARCH_X86_64
+#elif defined(__i386__)
+#define ARCH AUDIT_ARCH_I386
+#else
+#endif
+
+#ifdef ARCH
+/* Returns EPERM when trying to close fd 999 */
+SEC("seccomp")
+int bpf_prog1(struct seccomp_data *ctx)
+{
+ /*
+ * Make sure this BPF program is being run on the same architecture it
+ * was compiled on.
+ */
+ if (ctx->arch != ARCH)
+ return SECCOMP_RET_ERRNO | EPERM;
+ if (ctx->nr == __NR_close && ctx->args[0] == 999)
+ return SECCOMP_RET_ERRNO | EPERM;
+
+ return SECCOMP_RET_ALLOW;
+}
+#else
+#warning Architecture not supported -- Blocking all syscalls
+SEC("seccomp")
+int bpf_prog1(struct seccomp_data *ctx)
+{
+ return SECCOMP_RET_ERRNO | EPERM;
+}
+#endif
+
+
+
+
+char _license[] SEC("license") = "GPL";
diff --git a/samples/bpf/seccomp1_user.c b/samples/bpf/seccomp1_user.c
new file mode 100644
index 000000000000..b4951e0ca56f
--- /dev/null
+++ b/samples/bpf/seccomp1_user.c
@@ -0,0 +1,45 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <assert.h>
+#include <stdio.h>
+#include <linux/bpf.h>
+#include <unistd.h>
+#include "libbpf.h"
+#include "bpf_load.h"
+#include <linux/bpf.h>
+#include <sys/prctl.h>
+#include <strings.h>
+#include <errno.h>
+#include <linux/unistd.h>
+#include <linux/seccomp.h>
+
+int main(int argc, char **argv)
+{
+ char filename[256];
+
+
+ snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
+
+ if (load_bpf_file(filename)) {
+ printf("%s", bpf_log_buf);
+ return 1;
+ }
+
+ /* set new_new_privs so non-privileged users can attach filters */
+ if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
+ perror("prctl(NO_NEW_PRIVS)");
+ return 1;
+ }
+
+ if (syscall(__NR_seccomp, SECCOMP_SET_MODE_FILTER,
+ SECCOMP_FILTER_FLAG_EXTENDED, &prog_fd)) {
+ perror("seccomp");
+ return 1;
+ }
+
+ close(111);
+ assert(errno == EBADF);
+ close(999);
+ assert(errno = EPERM);
+
+ return 0;
+}
--
2.14.1
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