Re: [net-next v2 2/2] bpf: Add eBPF seccomp sample programs

[Sargun Dhillon]

On Sat, Feb 17, 2018 at 9:58 AM, Randy Dunlap  wrote:
> On 02/16/2018 11:36 PM, Sargun Dhillon wrote:
>> + close(111);
>> + assert(errno == EBADF);
>> + close(999);
>> + assert(errno = EPERM);
>
> should that be   == ?
>
Woops. Embarassing. Will fix that in the next re-spin.
>> +
>> + return 0;
>> +}
>
>
> --
> ~Randy

Re: [net-next v2 2/2] bpf: Add eBPF seccomp sample programs

[Randy Dunlap]

On 02/16/2018 11:36 PM, Sargun Dhillon wrote:
> + close(111);
> + assert(errno == EBADF);
> + close(999);
> + assert(errno = EPERM);

should that be   == ?

> +
> + return 0;
> +}


-- 
~Randy

[net-next v2 2/2] bpf: Add eBPF seccomp sample programs

[Sargun Dhillon]

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 
---
 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 ..420e37eebd92
--- /dev/null
+++ b/samples/bpf/seccomp1_kern.c
@@ -0,0 +1,43 @@
+#include 
+#include 
+#include 
+#include "bpf_helpers.h"
+#include 
+#include 
+
+#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