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Message-Id: <20220328181644.1748789-8-sdf@google.com>
Date: Mon, 28 Mar 2022 11:16:44 -0700
From: Stanislav Fomichev <sdf@...gle.com>
To: netdev@...r.kernel.org, bpf@...r.kernel.org
Cc: ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
Stanislav Fomichev <sdf@...gle.com>
Subject: [PATCH bpf-next 7/7] selftests/bpf: verify lsm_cgroup struct sock access
sk_priority & sk_mark are writable, the rest is readonly.
Add new ldx_offset fixups to lookup the offset of struct field.
Allow using test.kfunc regardless of prog_type.
One interesting thing here is that the verifier doesn't
really force me to add NULL checks anywhere :-/
Signed-off-by: Stanislav Fomichev <sdf@...gle.com>
---
tools/testing/selftests/bpf/test_verifier.c | 54 ++++++++++++++++++-
.../selftests/bpf/verifier/lsm_cgroup.c | 34 ++++++++++++
2 files changed, 87 insertions(+), 1 deletion(-)
create mode 100644 tools/testing/selftests/bpf/verifier/lsm_cgroup.c
diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
index a2cd236c32eb..d6bc55c54aaa 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -75,6 +75,12 @@ struct kfunc_btf_id_pair {
int insn_idx;
};
+struct ldx_offset {
+ const char *strct;
+ const char *field;
+ int insn_idx;
+};
+
struct bpf_test {
const char *descr;
struct bpf_insn insns[MAX_INSNS];
@@ -102,6 +108,7 @@ struct bpf_test {
int fixup_map_ringbuf[MAX_FIXUPS];
int fixup_map_timer[MAX_FIXUPS];
struct kfunc_btf_id_pair fixup_kfunc_btf_id[MAX_FIXUPS];
+ struct ldx_offset fixup_ldx[MAX_FIXUPS];
/* Expected verifier log output for result REJECT or VERBOSE_ACCEPT.
* Can be a tab-separated sequence of expected strings. An empty string
* means no log verification.
@@ -755,6 +762,7 @@ static void do_test_fixup(struct bpf_test *test, enum bpf_prog_type prog_type,
int *fixup_map_ringbuf = test->fixup_map_ringbuf;
int *fixup_map_timer = test->fixup_map_timer;
struct kfunc_btf_id_pair *fixup_kfunc_btf_id = test->fixup_kfunc_btf_id;
+ struct ldx_offset *fixup_ldx = test->fixup_ldx;
if (test->fill_helper) {
test->fill_insns = calloc(MAX_TEST_INSNS, sizeof(struct bpf_insn));
@@ -967,6 +975,50 @@ static void do_test_fixup(struct bpf_test *test, enum bpf_prog_type prog_type,
fixup_kfunc_btf_id++;
} while (fixup_kfunc_btf_id->kfunc);
}
+
+ if (fixup_ldx->strct) {
+ const struct btf_member *memb;
+ const struct btf_type *tp;
+ const char *name;
+ struct btf *btf;
+ int btf_id;
+ int off;
+ int i;
+
+ btf = btf__load_vmlinux_btf();
+
+ do {
+ off = -1;
+ if (!btf)
+ goto next_ldx;
+
+ btf_id = btf__find_by_name_kind(btf,
+ fixup_ldx->strct,
+ BTF_KIND_STRUCT);
+ if (btf_id < 0)
+ goto next_ldx;
+
+ tp = btf__type_by_id(btf, btf_id);
+ memb = btf_members(tp);
+
+ for (i = 0; i < btf_vlen(tp); i++) {
+ name = btf__name_by_offset(btf,
+ memb->name_off);
+ if (strcmp(fixup_ldx->field, name) == 0) {
+ off = memb->offset / 8;
+ break;
+ }
+ memb++;
+ }
+
+next_ldx:
+ prog[fixup_ldx->insn_idx].off = off;
+ fixup_ldx++;
+
+ } while (fixup_ldx->strct);
+
+ btf__free(btf);
+ }
}
struct libcap {
@@ -1131,7 +1183,7 @@ static void do_test_single(struct bpf_test *test, bool unpriv,
opts.log_level = 4;
opts.prog_flags = pflags;
- if (prog_type == BPF_PROG_TYPE_TRACING && test->kfunc) {
+ if (test->kfunc) {
int attach_btf_id;
attach_btf_id = libbpf_find_vmlinux_btf_id(test->kfunc,
diff --git a/tools/testing/selftests/bpf/verifier/lsm_cgroup.c b/tools/testing/selftests/bpf/verifier/lsm_cgroup.c
new file mode 100644
index 000000000000..af0efe783511
--- /dev/null
+++ b/tools/testing/selftests/bpf/verifier/lsm_cgroup.c
@@ -0,0 +1,34 @@
+#define SK_WRITABLE_FIELD(tp, field, size, res) \
+{ \
+ .descr = field, \
+ .insns = { \
+ /* r1 = *(u64 *)(r1 + 0) */ \
+ BPF_LDX_MEM(BPF_DW, BPF_REG_1, BPF_REG_1, 0), \
+ /* r1 = *(u64 *)(r1 + offsetof(struct socket, sk)) */ \
+ BPF_LDX_MEM(BPF_DW, BPF_REG_1, BPF_REG_1, 0), \
+ /* r2 = *(u64 *)(r1 + offsetof(struct sock, <field>)) */ \
+ BPF_LDX_MEM(size, BPF_REG_2, BPF_REG_1, 0), \
+ /* *(u64 *)(r1 + offsetof(struct sock, <field>)) = r2 */ \
+ BPF_STX_MEM(size, BPF_REG_1, BPF_REG_2, 0), \
+ BPF_MOV64_IMM(BPF_REG_0, 1), \
+ BPF_EXIT_INSN(), \
+ }, \
+ .result = res, \
+ .errstr = res ? "no write support to 'struct sock' at off" : "", \
+ .prog_type = BPF_PROG_TYPE_LSM, \
+ .expected_attach_type = BPF_LSM_CGROUP, \
+ .kfunc = "socket_post_create", \
+ .fixup_ldx = { \
+ { "socket", "sk", 1 }, \
+ { tp, field, 2 }, \
+ { tp, field, 3 }, \
+ }, \
+}
+
+SK_WRITABLE_FIELD("sock_common", "skc_family", BPF_H, REJECT),
+SK_WRITABLE_FIELD("sock", "sk_sndtimeo", BPF_DW, REJECT),
+SK_WRITABLE_FIELD("sock", "sk_priority", BPF_W, ACCEPT),
+SK_WRITABLE_FIELD("sock", "sk_mark", BPF_W, ACCEPT),
+SK_WRITABLE_FIELD("sock", "sk_pacing_rate", BPF_DW, REJECT),
+
+#undef SK_WRITABLE_FIELD
--
2.35.1.1021.g381101b075-goog
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