From e42ac14180554fa23a3312d4f921dc4ea7972fb7 Mon Sep 17 00:00:00 2001 From: Martin KaFai Lau Date: Mon, 22 Jul 2024 11:30:45 -0700 Subject: [PATCH 1/3] bpf: Check unsupported ops from the bpf_struct_ops's cfi_stubs 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 Signed-off-by: Martin KaFai Lau Link: https://lore.kernel.org/r/20240722183049.2254692-2-martin.lau@linux.dev Signed-off-by: Alexei Starovoitov Signed-off-by: Andrii Nakryiko --- 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 3b94ec161e8c..4c54864316ee 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..fda3dd2ee984 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 f8c474e8e597..247a038d3a14 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, From e44b4fc40cb429f6dedc4518a16221115035f654 Mon Sep 17 00:00:00 2001 From: Martin KaFai Lau Date: Mon, 22 Jul 2024 11:30:46 -0700 Subject: [PATCH 2/3] selftests/bpf: Fix the missing tramp_1 to tramp_40 ops in cfi_stubs 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 Link: https://lore.kernel.org/r/20240722183049.2254692-3-martin.lau@linux.dev Signed-off-by: Alexei Starovoitov Signed-off-by: Andrii Nakryiko --- .../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 fd28c1157bd3..3687a40b61c6 100644 --- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c +++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c @@ -1024,6 +1024,11 @@ 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) { @@ -1080,6 +1085,7 @@ 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); @@ -1103,6 +1109,14 @@ static int bpf_testmod_init(void) ret = register_bpf_testmod_uprobe(); if (ret < 0) return ret; + + /* 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 0; } From 4009c95fede6b783802ad01f264a7a0541f5ea60 Mon Sep 17 00:00:00 2001 From: Martin KaFai Lau Date: Mon, 22 Jul 2024 11:30:47 -0700 Subject: [PATCH 3/3] selftests/bpf: Ensure the unsupported struct_ops prog cannot be loaded 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 Link: https://lore.kernel.org/r/20240722183049.2254692-4-martin.lau@linux.dev Signed-off-by: Alexei Starovoitov Signed-off-by: Andrii Nakryiko --- .../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 +#include +#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, +};