* [PATCH bpf-next 1/3] bpf: Check unsupported ops from the bpf_struct_ops's cfi_stubs
2024-07-20 6:22 [PATCH bpf-next 0/3] bpf: Retire the unsupported_ops usage in struct_ops Martin KaFai Lau
@ 2024-07-20 6:22 ` Martin KaFai Lau
2024-07-20 14:45 ` kernel test robot
2024-07-20 6:22 ` [PATCH bpf-next 2/3] selftests/bpf: Fix the missing tramp_1 to tramp_40 ops in cfi_stubs Martin KaFai Lau
` (2 subsequent siblings)
3 siblings, 1 reply; 8+ messages in thread
From: Martin KaFai Lau @ 2024-07-20 6:22 UTC (permalink / raw)
To: bpf
Cc: Alexei Starovoitov, Andrii Nakryiko, Daniel Borkmann, kernel-team,
Amery Hung
From: Martin KaFai Lau <martin.lau@kernel.org>
The bpf_tcp_ca struct_ops currently uses a "u32 unsupported_ops[]"
array to track which ops is not supported.
After cfi_stubs had been added, the function pointer in cfi_stubs is
also NULL for the unsupported ops. Thus, the "u32 unsupported_ops[]"
becomes redundant. This observation was originally brought up in the
bpf/cfi discussion:
https://lore.kernel.org/bpf/CAADnVQJoEkdjyCEJRPASjBw1QGsKYrF33QdMGc1RZa9b88bAEA@mail.gmail.com/
The recent bpf qdisc patch (https://lore.kernel.org/bpf/20240714175130.4051012-6-amery.hung@bytedance.com/)
also needs to specify quite many unsupported ops. It is a good time
to clean it up.
This patch removes the need of "u32 unsupported_ops[]" and tests for null-ness
in the cfi_stubs instead.
Testing the cfi_stubs is done in a new function bpf_struct_ops_supported().
The verifier will call bpf_struct_ops_supported() when loading the
struct_ops program. The ".check_member" is removed from the bpf_tcp_ca
in this patch. ".check_member" could still be useful for other subsytems
to enforce other restrictions (e.g. sched_ext checks for prog->sleepable).
To keep the same error return, ENOTSUPP is used.
Cc: Amery Hung <ameryhung@gmail.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
---
include/linux/bpf.h | 5 +++++
kernel/bpf/bpf_struct_ops.c | 7 +++++++
kernel/bpf/verifier.c | 10 +++++++++-
net/ipv4/bpf_tcp_ca.c | 26 --------------------------
4 files changed, 21 insertions(+), 27 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 4f1d4a97b9d1..6464dd78ea13 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1795,6 +1795,7 @@ struct bpf_struct_ops_common_value {
#define BPF_MODULE_OWNER ((void *)((0xeB9FUL << 2) + POISON_POINTER_DELTA))
bool bpf_struct_ops_get(const void *kdata);
void bpf_struct_ops_put(const void *kdata);
+int bpf_struct_ops_supported(const struct bpf_struct_ops *st_ops, u32 moff);
int bpf_struct_ops_map_sys_lookup_elem(struct bpf_map *map, void *key,
void *value);
int bpf_struct_ops_prepare_trampoline(struct bpf_tramp_links *tlinks,
@@ -1851,6 +1852,10 @@ static inline void bpf_module_put(const void *data, struct module *owner)
{
module_put(owner);
}
+static inline int bpf_struct_ops_supported(const struct bpf_struct_ops *st_ops, u32 moff)
+{
+ return -ENOTSUPP;
+}
static inline int bpf_struct_ops_map_sys_lookup_elem(struct bpf_map *map,
void *key,
void *value)
diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
index bb3eabc0dc76..93ade7072976 100644
--- a/kernel/bpf/bpf_struct_ops.c
+++ b/kernel/bpf/bpf_struct_ops.c
@@ -1040,6 +1040,13 @@ void bpf_struct_ops_put(const void *kdata)
bpf_map_put(&st_map->map);
}
+int bpf_struct_ops_supported(const struct bpf_struct_ops *st_ops, u32 moff)
+{
+ void *func_ptr = *(void **)(&st_ops->cfi_stubs[moff]);
+
+ return func_ptr ? 0 : -ENOTSUPP;
+}
+
static bool bpf_struct_ops_valid_to_reg(struct bpf_map *map)
{
struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map *)map;
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 656766dd76df..33cb57c20d78 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -21132,6 +21132,7 @@ static int check_struct_ops_btf_id(struct bpf_verifier_env *env)
u32 btf_id, member_idx;
struct btf *btf;
const char *mname;
+ int err;
if (!prog->gpl_compatible) {
verbose(env, "struct ops programs must have a GPL compatible license\n");
@@ -21179,8 +21180,15 @@ static int check_struct_ops_btf_id(struct bpf_verifier_env *env)
return -EINVAL;
}
+ err = bpf_struct_ops_supported(st_ops, __btf_member_bit_offset(t, member) / 8);
+ if (err) {
+ verbose(env, "attach to unsupported member %s of struct %s\n",
+ mname, st_ops->name);
+ return err;
+ }
+
if (st_ops->check_member) {
- int err = st_ops->check_member(t, member, prog);
+ err = st_ops->check_member(t, member, prog);
if (err) {
verbose(env, "attach to unsupported member %s of struct %s\n",
diff --git a/net/ipv4/bpf_tcp_ca.c b/net/ipv4/bpf_tcp_ca.c
index 3f88d0961e5b..554804774628 100644
--- a/net/ipv4/bpf_tcp_ca.c
+++ b/net/ipv4/bpf_tcp_ca.c
@@ -14,10 +14,6 @@
/* "extern" is to avoid sparse warning. It is only used in bpf_struct_ops.c. */
static struct bpf_struct_ops bpf_tcp_congestion_ops;
-static u32 unsupported_ops[] = {
- offsetof(struct tcp_congestion_ops, get_info),
-};
-
static const struct btf_type *tcp_sock_type;
static u32 tcp_sock_id, sock_id;
static const struct btf_type *tcp_congestion_ops_type;
@@ -45,18 +41,6 @@ static int bpf_tcp_ca_init(struct btf *btf)
return 0;
}
-static bool is_unsupported(u32 member_offset)
-{
- unsigned int i;
-
- for (i = 0; i < ARRAY_SIZE(unsupported_ops); i++) {
- if (member_offset == unsupported_ops[i])
- return true;
- }
-
- return false;
-}
-
static bool bpf_tcp_ca_is_valid_access(int off, int size,
enum bpf_access_type type,
const struct bpf_prog *prog,
@@ -251,15 +235,6 @@ static int bpf_tcp_ca_init_member(const struct btf_type *t,
return 0;
}
-static int bpf_tcp_ca_check_member(const struct btf_type *t,
- const struct btf_member *member,
- const struct bpf_prog *prog)
-{
- if (is_unsupported(__btf_member_bit_offset(t, member) / 8))
- return -ENOTSUPP;
- return 0;
-}
-
static int bpf_tcp_ca_reg(void *kdata, struct bpf_link *link)
{
return tcp_register_congestion_control(kdata);
@@ -354,7 +329,6 @@ static struct bpf_struct_ops bpf_tcp_congestion_ops = {
.reg = bpf_tcp_ca_reg,
.unreg = bpf_tcp_ca_unreg,
.update = bpf_tcp_ca_update,
- .check_member = bpf_tcp_ca_check_member,
.init_member = bpf_tcp_ca_init_member,
.init = bpf_tcp_ca_init,
.validate = bpf_tcp_ca_validate,
--
2.43.0
^ permalink raw reply related [flat|nested] 8+ messages in thread* [PATCH bpf-next 2/3] selftests/bpf: Fix the missing tramp_1 to tramp_40 ops in cfi_stubs
2024-07-20 6:22 [PATCH bpf-next 0/3] bpf: Retire the unsupported_ops usage in struct_ops Martin KaFai Lau
2024-07-20 6:22 ` [PATCH bpf-next 1/3] bpf: Check unsupported ops from the bpf_struct_ops's cfi_stubs Martin KaFai Lau
@ 2024-07-20 6:22 ` Martin KaFai Lau
2024-07-20 6:22 ` [PATCH bpf-next 3/3] selftests/bpf: Ensure the unsupported struct_ops prog cannot be loaded Martin KaFai Lau
2024-07-20 6:43 ` [PATCH bpf-next 0/3] bpf: Retire the unsupported_ops usage in struct_ops bot+bpf-ci
3 siblings, 0 replies; 8+ messages in thread
From: Martin KaFai Lau @ 2024-07-20 6:22 UTC (permalink / raw)
To: bpf; +Cc: Alexei Starovoitov, Andrii Nakryiko, Daniel Borkmann, kernel-team
From: Martin KaFai Lau <martin.lau@kernel.org>
The tramp_1 to tramp_40 ops is not set in the cfi_stubs in the
bpf_testmod_ops. It fails the struct_ops_multi_pages test after
retiring the unsupported_ops in the earlier patch.
This patch initializes them in a loop during the bpf_testmod_init().
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
---
.../selftests/bpf/bpf_testmod/bpf_testmod.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
index f8962a1dd397..fb951a1d91d5 100644
--- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
+++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
@@ -910,6 +910,11 @@ static void bpf_testmod_test_2(int a, int b)
{
}
+static int bpf_testmod_tramp(int value)
+{
+ return 0;
+}
+
static int bpf_testmod_ops__test_maybe_null(int dummy,
struct task_struct *task__nullable)
{
@@ -966,6 +971,7 @@ static int bpf_testmod_init(void)
.kfunc_btf_id = bpf_testmod_dtor_ids[1]
},
};
+ void **tramp;
int ret;
ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_UNSPEC, &bpf_testmod_common_kfunc_set);
@@ -983,6 +989,14 @@ static int bpf_testmod_init(void)
return -EINVAL;
sock = NULL;
mutex_init(&sock_lock);
+
+ /* Ensure nothing is between tramp_1..tramp_40 */
+ BUILD_BUG_ON(offsetof(struct bpf_testmod_ops, tramp_1) + 40 * sizeof(long) !=
+ offsetofend(struct bpf_testmod_ops, tramp_40));
+ tramp = (void **)&__bpf_testmod_ops.tramp_1;
+ while (tramp <= (void **)&__bpf_testmod_ops.tramp_40)
+ *tramp++ = bpf_testmod_tramp;
+
return sysfs_create_bin_file(kernel_kobj, &bin_attr_bpf_testmod_file);
}
--
2.43.0
^ permalink raw reply related [flat|nested] 8+ messages in thread* [PATCH bpf-next 3/3] selftests/bpf: Ensure the unsupported struct_ops prog cannot be loaded
2024-07-20 6:22 [PATCH bpf-next 0/3] bpf: Retire the unsupported_ops usage in struct_ops Martin KaFai Lau
2024-07-20 6:22 ` [PATCH bpf-next 1/3] bpf: Check unsupported ops from the bpf_struct_ops's cfi_stubs Martin KaFai Lau
2024-07-20 6:22 ` [PATCH bpf-next 2/3] selftests/bpf: Fix the missing tramp_1 to tramp_40 ops in cfi_stubs Martin KaFai Lau
@ 2024-07-20 6:22 ` Martin KaFai Lau
2024-07-20 6:43 ` [PATCH bpf-next 0/3] bpf: Retire the unsupported_ops usage in struct_ops bot+bpf-ci
3 siblings, 0 replies; 8+ messages in thread
From: Martin KaFai Lau @ 2024-07-20 6:22 UTC (permalink / raw)
To: bpf; +Cc: Alexei Starovoitov, Andrii Nakryiko, Daniel Borkmann, kernel-team
From: Martin KaFai Lau <martin.lau@kernel.org>
There is an existing "bpf_tcp_ca/unsupp_cong_op" test to ensure
the unsupported tcp-cc "get_info" struct_ops prog cannot be loaded.
This patch adds a new test in the bpf_testmod such that the
unsupported ops test does not depend on other kernel subsystem
where its supporting ops may be changed in the future.
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
---
.../selftests/bpf/bpf_testmod/bpf_testmod.h | 1 +
.../bpf/prog_tests/test_struct_ops_module.c | 2 ++
.../selftests/bpf/progs/unsupported_ops.c | 22 +++++++++++++++++++
3 files changed, 25 insertions(+)
create mode 100644 tools/testing/selftests/bpf/progs/unsupported_ops.c
diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.h b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.h
index 23fa1872ee67..fe0d402b0d65 100644
--- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.h
+++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.h
@@ -35,6 +35,7 @@ struct bpf_testmod_ops {
void (*test_2)(int a, int b);
/* Used to test nullable arguments. */
int (*test_maybe_null)(int dummy, struct task_struct *task);
+ int (*unsupported_ops)(void);
/* The following fields are used to test shadow copies. */
char onebyte;
diff --git a/tools/testing/selftests/bpf/prog_tests/test_struct_ops_module.c b/tools/testing/selftests/bpf/prog_tests/test_struct_ops_module.c
index bbcf12696a6b..75a0dea511b3 100644
--- a/tools/testing/selftests/bpf/prog_tests/test_struct_ops_module.c
+++ b/tools/testing/selftests/bpf/prog_tests/test_struct_ops_module.c
@@ -9,6 +9,7 @@
#include "struct_ops_nulled_out_cb.skel.h"
#include "struct_ops_forgotten_cb.skel.h"
#include "struct_ops_detach.skel.h"
+#include "unsupported_ops.skel.h"
static void check_map_info(struct bpf_map_info *info)
{
@@ -311,5 +312,6 @@ void serial_test_struct_ops_module(void)
test_struct_ops_forgotten_cb();
if (test__start_subtest("test_detach_link"))
test_detach_link();
+ RUN_TESTS(unsupported_ops);
}
diff --git a/tools/testing/selftests/bpf/progs/unsupported_ops.c b/tools/testing/selftests/bpf/progs/unsupported_ops.c
new file mode 100644
index 000000000000..9180365a3568
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/unsupported_ops.c
@@ -0,0 +1,22 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2024 Meta Platforms, Inc. and affiliates. */
+
+#include <vmlinux.h>
+#include <bpf/bpf_tracing.h>
+#include "bpf_misc.h"
+#include "../bpf_testmod/bpf_testmod.h"
+
+char _license[] SEC("license") = "GPL";
+
+SEC("struct_ops/unsupported_ops")
+__failure
+__msg("attach to unsupported member unsupported_ops of struct bpf_testmod_ops")
+int BPF_PROG(unsupported_ops)
+{
+ return 0;
+}
+
+SEC(".struct_ops.link")
+struct bpf_testmod_ops testmod = {
+ .unsupported_ops = (void *)unsupported_ops,
+};
--
2.43.0
^ permalink raw reply related [flat|nested] 8+ messages in thread