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Subject[PATCH bpf-next v9 02/10] bpf: Add eBPF program subtype and is_valid_subtype() verifier
Date
The goal of the program subtype is to be able to have different static
fine-grained verifications for a unique program type.

The struct bpf_verifier_ops gets a new optional function:
is_valid_subtype(). This new verifier is called at the beginning of the
eBPF program verification to check if the (optional) program subtype is
valid.

The new helper bpf_load_program_xattr() enables to verify a program with
subtypes.

For now, only Landlock eBPF programs are using a program subtype (see
next commits) but this could be used by other program types in the
future.

Signed-off-by: Mickaël Salaün <mic@digikod.net>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: David S. Miller <davem@davemloft.net>
Link: https://lkml.kernel.org/r/20160827205559.GA43880@ast-mbp.thefacebook.com
---

Changes since v8:
* use bpf_load_program_xattr() instead of bpf_load_program() and add
bpf_verify_program_xattr() to deal with subtypes
* remove put_extra() since there is no more "previous" field (for now)

Changes since v7:
* rename LANDLOCK_SUBTYPE_* to LANDLOCK_*
* move subtype in bpf_prog_aux and use only one bit for has_subtype
(suggested by Alexei Starovoitov)
* wrap the prog_subtype with a prog_extra to be able to reference kernel
pointers:
* add an optional put_extra() function to struct bpf_prog_ops to be
able to free the pointed data
* replace all the prog_subtype with prog_extra in the struct
bpf_verifier_ops functions
* remove the ABI field (requested by Alexei Starovoitov)
* rename subtype fields

Changes since v6:
* rename Landlock version to ABI to better reflect its purpose
* fix unsigned integer checks
* fix pointer cast
* constify pointers
* rebase

Changes since v5:
* use a prog_subtype pointer and make it future-proof
* add subtype test
* constify bpf_load_program()'s subtype argument
* cleanup subtype initialization
* rebase

Changes since v4:
* replace the "status" field with "version" (more generic)
* replace the "access" field with "ability" (less confusing)

Changes since v3:
* remove the "origin" field
* add an "option" field
* cleanup comments
---
include/linux/bpf.h | 8 +++++
include/uapi/linux/bpf.h | 9 ++++++
kernel/bpf/core.c | 1 +
kernel/bpf/syscall.c | 32 ++++++++++++++++++-
kernel/bpf/verifier.c | 11 +++++++
net/core/filter.c | 25 ++++++++-------
tools/include/uapi/linux/bpf.h | 9 ++++++
tools/lib/bpf/bpf.c | 10 +++++-
tools/lib/bpf/bpf.h | 2 ++
tools/lib/bpf/libbpf.map | 1 +
tools/testing/selftests/bpf/test_verifier.c | 26 +++++++++++++--
.../testing/selftests/bpf/verifier/subtype.c | 10 ++++++
12 files changed, 128 insertions(+), 16 deletions(-)
create mode 100644 tools/testing/selftests/bpf/verifier/subtype.c

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index a62e7889b0b6..da167d3afecc 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -294,6 +294,11 @@ bpf_ctx_record_field_size(struct bpf_insn_access_aux *aux, u32 size)
aux->ctx_field_size = size;
}

+/* specific data per program type */
+struct bpf_prog_extra {
+ union bpf_prog_subtype subtype;
+};
+
struct bpf_prog_ops {
int (*test_run)(struct bpf_prog *prog, const union bpf_attr *kattr,
union bpf_attr __user *uattr);
@@ -319,6 +324,8 @@ struct bpf_verifier_ops {
const struct bpf_insn *src,
struct bpf_insn *dst,
struct bpf_prog *prog, u32 *target_size);
+ // TODO?: convert to bool (*is_valid_subtype)(struct bpf_prog *prog);
+ bool (*is_valid_subtype)(struct bpf_prog_extra *prog_extra);
};

struct bpf_prog_offload_ops {
@@ -418,6 +425,7 @@ struct bpf_prog_aux {
struct work_struct work;
struct rcu_head rcu;
};
+ struct bpf_prog_extra *extra;
};

struct bpf_array {
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index b077507efa3f..ddae50373d58 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -355,6 +355,13 @@ struct bpf_stack_build_id {
};
};

+union bpf_prog_subtype {
+ struct {
+ __u32 type; /* enum landlock_hook_type */
+ __aligned_u64 triggers; /* LANDLOCK_TRIGGER_* */
+ } landlock_hook;
+} __attribute__((aligned(8)));
+
union bpf_attr {
struct { /* anonymous struct used by BPF_MAP_CREATE command */
__u32 map_type; /* one of enum bpf_map_type */
@@ -409,6 +416,8 @@ union bpf_attr {
__u32 line_info_rec_size; /* userspace bpf_line_info size */
__aligned_u64 line_info; /* line info */
__u32 line_info_cnt; /* number of bpf_line_info records */
+ __aligned_u64 prog_subtype; /* bpf_prog_subtype address */
+ __u32 prog_subtype_size;
};

struct { /* anonymous struct used by BPF_OBJ_* commands */
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index ad3be85f1411..8ad392e52328 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -255,6 +255,7 @@ void __bpf_prog_free(struct bpf_prog *fp)
{
if (fp->aux) {
free_percpu(fp->aux->stats);
+ kfree(fp->aux->extra);
kfree(fp->aux);
}
vfree(fp);
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 7713cf39795a..7dd3376904d4 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1596,7 +1596,7 @@ bpf_prog_load_check_attach_type(enum bpf_prog_type prog_type,
}

/* last field in 'union bpf_attr' used by this command */
-#define BPF_PROG_LOAD_LAST_FIELD line_info_cnt
+#define BPF_PROG_LOAD_LAST_FIELD prog_subtype_size

static int bpf_prog_load(union bpf_attr *attr, union bpf_attr __user *uattr)
{
@@ -1686,6 +1686,36 @@ static int bpf_prog_load(union bpf_attr *attr, union bpf_attr __user *uattr)
if (err)
goto free_prog;

+ /* copy eBPF program subtype from user space */
+ if (attr->prog_subtype) {
+ u32 size;
+
+ err = bpf_check_uarg_tail_zero(
+ u64_to_user_ptr(attr->prog_subtype),
+ sizeof(prog->aux->extra->subtype),
+ attr->prog_subtype_size);
+ if (err)
+ goto free_prog;
+ size = min_t(u32, attr->prog_subtype_size,
+ sizeof(prog->aux->extra->subtype));
+
+ prog->aux->extra = kzalloc(sizeof(*prog->aux->extra),
+ GFP_KERNEL | GFP_USER);
+ if (!prog->aux->extra) {
+ err = -ENOMEM;
+ goto free_prog;
+ }
+ if (copy_from_user(&prog->aux->extra->subtype,
+ u64_to_user_ptr(attr->prog_subtype), size)
+ != 0) {
+ err = -EFAULT;
+ goto free_prog;
+ }
+ } else if (attr->prog_subtype_size != 0) {
+ err = -EINVAL;
+ goto free_prog;
+ }
+
/* run eBPF verifier */
err = bpf_check(&prog, attr, uattr);
if (err < 0)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 0e079b2298f8..930260683d0a 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -9167,6 +9167,17 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr,
if (ret < 0)
goto skip_full_check;

+ if (env->ops->is_valid_subtype) {
+ if (!env->ops->is_valid_subtype(env->prog->aux->extra)) {
+ ret = -EINVAL;
+ goto err_unlock;
+ }
+ } else if (env->prog->aux->extra) {
+ /* do not accept a subtype if the program does not handle it */
+ ret = -EINVAL;
+ goto err_unlock;
+ }
+
if (bpf_prog_is_dev_bound(env->prog->aux)) {
ret = bpf_prog_offload_verifier_prep(env->prog);
if (ret)
diff --git a/net/core/filter.c b/net/core/filter.c
index 2014d76e0d2a..0160237e5cd8 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -5846,7 +5846,8 @@ bool bpf_helper_changes_pkt_data(void *func)
}

static const struct bpf_func_proto *
-bpf_base_func_proto(enum bpf_func_id func_id)
+bpf_base_func_proto(enum bpf_func_id func_id,
+ const struct bpf_prog_extra *prog_extra)
{
switch (func_id) {
case BPF_FUNC_map_lookup_elem:
@@ -5902,7 +5903,7 @@ sock_filter_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
case BPF_FUNC_get_local_storage:
return &bpf_get_local_storage_proto;
default:
- return bpf_base_func_proto(func_id);
+ return bpf_base_func_proto(func_id, prog->aux->extra);
}
}

@@ -5942,7 +5943,7 @@ sock_addr_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
case BPF_FUNC_sk_storage_delete:
return &bpf_sk_storage_delete_proto;
default:
- return bpf_base_func_proto(func_id);
+ return bpf_base_func_proto(func_id, prog->aux->extra);
}
}

@@ -5959,7 +5960,7 @@ sk_filter_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
case BPF_FUNC_get_socket_uid:
return &bpf_get_socket_uid_proto;
default:
- return bpf_base_func_proto(func_id);
+ return bpf_base_func_proto(func_id, prog->aux->extra);
}
}

@@ -6096,7 +6097,7 @@ tc_cls_act_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
return &bpf_skb_ecn_set_ce_proto;
#endif
default:
- return bpf_base_func_proto(func_id);
+ return bpf_base_func_proto(func_id, prog->aux->extra);
}
}

@@ -6135,7 +6136,7 @@ xdp_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
return &bpf_tcp_check_syncookie_proto;
#endif
default:
- return bpf_base_func_proto(func_id);
+ return bpf_base_func_proto(func_id, prog->aux->extra);
}
}

@@ -6171,7 +6172,7 @@ sock_ops_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
return &bpf_tcp_sock_proto;
#endif /* CONFIG_INET */
default:
- return bpf_base_func_proto(func_id);
+ return bpf_base_func_proto(func_id, prog->aux->extra);
}
}

@@ -6197,7 +6198,7 @@ sk_msg_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
case BPF_FUNC_msg_pop_data:
return &bpf_msg_pop_data_proto;
default:
- return bpf_base_func_proto(func_id);
+ return bpf_base_func_proto(func_id, prog->aux->extra);
}
}

@@ -6237,7 +6238,7 @@ sk_skb_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
return &bpf_skc_lookup_tcp_proto;
#endif
default:
- return bpf_base_func_proto(func_id);
+ return bpf_base_func_proto(func_id, prog->aux->extra);
}
}

@@ -6248,7 +6249,7 @@ flow_dissector_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
case BPF_FUNC_skb_load_bytes:
return &bpf_flow_dissector_load_bytes_proto;
default:
- return bpf_base_func_proto(func_id);
+ return bpf_base_func_proto(func_id, prog->aux->extra);
}
}

@@ -6275,7 +6276,7 @@ lwt_out_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
case BPF_FUNC_skb_under_cgroup:
return &bpf_skb_under_cgroup_proto;
default:
- return bpf_base_func_proto(func_id);
+ return bpf_base_func_proto(func_id, prog->aux->extra);
}
}

@@ -8611,7 +8612,7 @@ sk_reuseport_func_proto(enum bpf_func_id func_id,
case BPF_FUNC_skb_load_bytes_relative:
return &sk_reuseport_load_bytes_relative_proto;
default:
- return bpf_base_func_proto(func_id);
+ return bpf_base_func_proto(func_id, prog->aux->extra);
}
}

diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index b077507efa3f..ddae50373d58 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -355,6 +355,13 @@ struct bpf_stack_build_id {
};
};

+union bpf_prog_subtype {
+ struct {
+ __u32 type; /* enum landlock_hook_type */
+ __aligned_u64 triggers; /* LANDLOCK_TRIGGER_* */
+ } landlock_hook;
+} __attribute__((aligned(8)));
+
union bpf_attr {
struct { /* anonymous struct used by BPF_MAP_CREATE command */
__u32 map_type; /* one of enum bpf_map_type */
@@ -409,6 +416,8 @@ union bpf_attr {
__u32 line_info_rec_size; /* userspace bpf_line_info size */
__aligned_u64 line_info; /* line info */
__u32 line_info_cnt; /* number of bpf_line_info records */
+ __aligned_u64 prog_subtype; /* bpf_prog_subtype address */
+ __u32 prog_subtype_size;
};

struct { /* anonymous struct used by BPF_OBJ_* commands */
diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index c7d7993c44bb..ecd894344bbd 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -227,6 +227,9 @@ int bpf_load_program_xattr(const struct bpf_load_program_attr *load_attr,

memset(&attr, 0, sizeof(attr));
attr.prog_type = load_attr->prog_type;
+ attr.prog_subtype = ptr_to_u64(load_attr->prog_subtype);
+ attr.prog_subtype_size = load_attr->prog_subtype ?
+ sizeof(*load_attr->prog_subtype) : 0;
attr.expected_attach_type = load_attr->expected_attach_type;
attr.insn_cnt = (__u32)load_attr->insns_cnt;
attr.insns = ptr_to_u64(load_attr->insns);
@@ -332,6 +335,11 @@ int bpf_load_program(enum bpf_prog_type type, const struct bpf_insn *insns,
return bpf_load_program_xattr(&load_attr, log_buf, log_buf_sz);
}

+int bpf_verify_program_xattr(union bpf_attr *attr, size_t attr_sz)
+{
+ return sys_bpf_prog_load(attr, attr_sz);
+}
+
int bpf_verify_program(enum bpf_prog_type type, const struct bpf_insn *insns,
size_t insns_cnt, __u32 prog_flags, const char *license,
__u32 kern_version, char *log_buf, size_t log_buf_sz,
@@ -351,7 +359,7 @@ int bpf_verify_program(enum bpf_prog_type type, const struct bpf_insn *insns,
attr.kern_version = kern_version;
attr.prog_flags = prog_flags;

- return sys_bpf_prog_load(&attr, sizeof(attr));
+ return bpf_verify_program_xattr(&attr, sizeof(attr));
}

int bpf_map_update_elem(int fd, const void *key, const void *value,
diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
index ff42ca043dc8..7cd600d49f9e 100644
--- a/tools/lib/bpf/bpf.h
+++ b/tools/lib/bpf/bpf.h
@@ -88,6 +88,7 @@ struct bpf_load_program_attr {
__u32 line_info_cnt;
__u32 log_level;
__u32 prog_flags;
+ const union bpf_prog_subtype *prog_subtype;
};

/* Flags to direct loading requirements */
@@ -102,6 +103,7 @@ LIBBPF_API int bpf_load_program(enum bpf_prog_type type,
const struct bpf_insn *insns, size_t insns_cnt,
const char *license, __u32 kern_version,
char *log_buf, size_t log_buf_sz);
+LIBBPF_API int bpf_verify_program_xattr(union bpf_attr *attr, size_t attr_sz);
LIBBPF_API int bpf_verify_program(enum bpf_prog_type type,
const struct bpf_insn *insns,
size_t insns_cnt, __u32 prog_flags,
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 2c6d835620d2..48c9269a0496 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -107,6 +107,7 @@ LIBBPF_0.0.1 {
bpf_set_link_xdp_fd;
bpf_task_fd_query;
bpf_verify_program;
+ bpf_verify_program_xattr;
btf__fd;
btf__find_by_name;
btf__free;
diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
index c5514daf8865..93faffd31fc3 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -105,6 +105,8 @@ struct bpf_test {
__u64 data64[TEST_DATA_LEN / 8];
};
} retvals[MAX_TEST_RUNS];
+ bool has_prog_subtype;
+ union bpf_prog_subtype prog_subtype;
};

/* Note we want this to be 64 bit aligned so that the end of our array is
@@ -122,6 +124,11 @@ struct other_val {
long long bar;
};

+static inline __u64 ptr_to_u64(const void *ptr)
+{
+ return (__u64) (unsigned long) ptr;
+}
+
static void bpf_fill_ld_abs_vlan_push_pop(struct bpf_test *self)
{
/* test: {skb->data[0], vlan_push} x 51 + {skb->data[0], vlan_pop} x 51 */
@@ -856,6 +863,9 @@ static void do_test_single(struct bpf_test *test, bool unpriv,
int fixup_skips;
__u32 pflags;
int i, err;
+ union bpf_attr attr;
+ union bpf_prog_subtype *prog_subtype =
+ test->has_prog_subtype ? &test->prog_subtype : NULL;

for (i = 0; i < MAX_NR_MAPS; i++)
map_fds[i] = -1;
@@ -881,8 +891,20 @@ static void do_test_single(struct bpf_test *test, bool unpriv,
pflags |= BPF_F_STRICT_ALIGNMENT;
if (test->flags & F_NEEDS_EFFICIENT_UNALIGNED_ACCESS)
pflags |= BPF_F_ANY_ALIGNMENT;
- fd_prog = bpf_verify_program(prog_type, prog, prog_len, pflags,
- "GPL", 0, bpf_vlog, sizeof(bpf_vlog), 4);
+
+ memset(&attr, 0, sizeof(attr));
+ attr.prog_type = prog_type;
+ attr.prog_subtype = ptr_to_u64(prog_subtype);
+ attr.prog_subtype_size = prog_subtype ? sizeof(*prog_subtype) : 0;
+ attr.insn_cnt = (__u32)prog_len;
+ attr.insns = ptr_to_u64(prog);
+ attr.license = ptr_to_u64("GPL");
+ bpf_vlog[0] = 0;
+ attr.log_buf = ptr_to_u64(bpf_vlog);
+ attr.log_size = sizeof(bpf_vlog);
+ attr.log_level = 4;
+ attr.prog_flags = pflags;
+ fd_prog = bpf_verify_program_xattr(&attr, sizeof(attr));
if (fd_prog < 0 && !bpf_probe_prog_type(prog_type, 0)) {
printf("SKIP (unsupported program type %d)\n", prog_type);
skips++;
diff --git a/tools/testing/selftests/bpf/verifier/subtype.c b/tools/testing/selftests/bpf/verifier/subtype.c
new file mode 100644
index 000000000000..cf614223d53f
--- /dev/null
+++ b/tools/testing/selftests/bpf/verifier/subtype.c
@@ -0,0 +1,10 @@
+{
+ "superfluous subtype",
+ .insns = {
+ BPF_MOV32_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ },
+ .errstr = "",
+ .result = REJECT,
+ .has_prog_subtype = true,
+},
--
2.20.1
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