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Tue, 17 Mar 2026 04:18:57 -0700 (PDT) Received: from localhost ([2a03:2880:10ff:46::]) by smtp.gmail.com with ESMTPSA id 5614622812f47-46734123939sm11190975b6e.3.2026.03.17.04.18.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 17 Mar 2026 04:18:55 -0700 (PDT) From: Kumar Kartikeya Dwivedi To: bpf@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Martin KaFai Lau , Eduard Zingerman , Tejun Heo , Dan Schatzberg , kkd@meta.com, kernel-team@meta.com Subject: [PATCH bpf-next v1 2/4] selftests/bpf: Adjust syscall ctx variable offset tests Date: Tue, 17 Mar 2026 04:18:47 -0700 Message-ID: <20260317111850.2107846-3-memxor@gmail.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260317111850.2107846-1-memxor@gmail.com> References: <20260317111850.2107846-1-memxor@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=17033; h=from:subject; bh=Uqwysqa4YQf17vCw7Ai0DC3ilNtmo/saShotUw4BYQ0=; b=owEBbQKS/ZANAwAIAUzgyIZIvxHKAcsmYgBpuTHipysVkc4VhXHe5Njcy9FNPPTGZ8G0+qmmrJWO asMtTDCJAjMEAAEIAB0WIQRLvip+Buz51YI8YRFM4MiGSL8RygUCabkx4gAKCRBM4MiGSL8RyiI4D/ 9jM8HcX8hKlkEz/ylWbJll68zqlEWFI4lbYWBhtqCdXxcd8pA87PeCzGqhUANwofzChvirYN+0PMX5 N2TNT9+dVVJIYhepAuZUjV7S8gZOyZX4PJWqTCsbjmDFIsNUHZavQDiELGW/5ny6BvxKOPnxyo/NEF 41G8T0J0n4lHZUaU/VrmhzOftefHqrG2qyJulDwpQb7KmwORgNTXywp2XyQwHeFtgYJ9tKO3WLOzib 9nQojx0PMqkR9grOLyWxq7L23QWmtDBZSdgfYjwRS3MijFrFsMgk9bBXDfbfjVPk/9Vy7YGmDmdhSi K2HTVs8/7yk5tA3RrWAHZFswf1qZHACSxSFQwGe91Mk2XWY2v4jhDpGYR/oFAre2YRUfmvoi6kqNIo +DJZwzniIlM2q1ObC1tv1GcbzgN2Qqnni6nowESpc/fOU5L84LCnKfQr8kv1Q42RtJIdStZBO02g6L t866B08dxJPV6ov9oNTZPc36lvndVU73BGUQ1zW7v6GfApGPqitPeK2E1JFk1MQWoJa+tAQ0wynT60 GwEzFmnloytMzyk7EyRtoRQfDHmZcraUmSu0bWk3q1G8FuDKfarJ/v+MCke1gemRPL7GP/2LZTAxs7 2llgv5kDOuJ9tJCjjgEdUBas/lcdwKxmNLhrd39MEwCxTdahxynAjuvn8anQ== X-Developer-Key: i=memxor@gmail.com; a=openpgp; fpr=4BBE2A7E06ECF9D5823C61114CE0C88648BF11CA Content-Transfer-Encoding: 8bit Add various tests to exercise fixed and variable offsets on PTR_TO_CTX for syscall programs, and cover disallowed cases for other program types lacking convert_ctx_access callback. Load verifier_ctx with CAP_SYS_ADMIN so that kfunc related logic can be tested. While at it, convert assembly tests to C. Signed-off-by: Kumar Kartikeya Dwivedi --- .../selftests/bpf/prog_tests/verifier.c | 34 +- .../selftests/bpf/progs/verifier_ctx.c | 356 +++++++++++++++--- .../selftests/bpf/test_kmods/bpf_testmod.c | 2 +- 3 files changed, 325 insertions(+), 67 deletions(-) diff --git a/tools/testing/selftests/bpf/prog_tests/verifier.c b/tools/testing/selftests/bpf/prog_tests/verifier.c index 8cdfd74c95d7..04d5f46264a3 100644 --- a/tools/testing/selftests/bpf/prog_tests/verifier.c +++ b/tools/testing/selftests/bpf/prog_tests/verifier.c @@ -126,29 +126,35 @@ struct test_val { __maybe_unused static void run_tests_aux(const char *skel_name, skel_elf_bytes_fn elf_bytes_factory, - pre_execution_cb pre_execution_cb) + pre_execution_cb pre_execution_cb, + bool drop_sys_admin) { struct test_loader tester = {}; __u64 old_caps; int err; - /* test_verifier tests are executed w/o CAP_SYS_ADMIN, do the same here */ - err = cap_disable_effective(1ULL << CAP_SYS_ADMIN, &old_caps); - if (err) { - PRINT_FAIL("failed to drop CAP_SYS_ADMIN: %i, %s\n", err, strerror(-err)); - return; + if (drop_sys_admin) { + /* test_verifier tests are executed w/o CAP_SYS_ADMIN, do the same here */ + err = cap_disable_effective(1ULL << CAP_SYS_ADMIN, &old_caps); + if (err) { + PRINT_FAIL("failed to drop CAP_SYS_ADMIN: %i, %s\n", err, strerror(-err)); + return; + } } test_loader__set_pre_execution_cb(&tester, pre_execution_cb); test_loader__run_subtests(&tester, skel_name, elf_bytes_factory); test_loader_fini(&tester); - err = cap_enable_effective(old_caps, NULL); - if (err) - PRINT_FAIL("failed to restore CAP_SYS_ADMIN: %i, %s\n", err, strerror(-err)); + if (drop_sys_admin) { + err = cap_enable_effective(old_caps, NULL); + if (err) + PRINT_FAIL("failed to restore CAP_SYS_ADMIN: %i, %s\n", err, strerror(-err)); + } } -#define RUN(skel) run_tests_aux(#skel, skel##__elf_bytes, NULL) +#define RUN(skel) run_tests_aux(#skel, skel##__elf_bytes, NULL, true) +#define RUN_WITH_CAP_SYS_ADMIN(skel) run_tests_aux(#skel, skel##__elf_bytes, NULL, false) void test_verifier_align(void) { RUN(verifier_align); } void test_verifier_and(void) { RUN(verifier_and); } @@ -173,7 +179,7 @@ void test_verifier_cgroup_skb(void) { RUN(verifier_cgroup_skb); } void test_verifier_cgroup_storage(void) { RUN(verifier_cgroup_storage); } void test_verifier_const(void) { RUN(verifier_const); } void test_verifier_const_or(void) { RUN(verifier_const_or); } -void test_verifier_ctx(void) { RUN(verifier_ctx); } +void test_verifier_ctx(void) { RUN_WITH_CAP_SYS_ADMIN(verifier_ctx); } void test_verifier_ctx_sk_msg(void) { RUN(verifier_ctx_sk_msg); } void test_verifier_d_path(void) { RUN(verifier_d_path); } void test_verifier_default_trusted_ptr(void) { RUN_TESTS(verifier_default_trusted_ptr); } @@ -293,7 +299,8 @@ void test_verifier_array_access(void) { run_tests_aux("verifier_array_access", verifier_array_access__elf_bytes, - init_array_access_maps); + init_array_access_maps, + true); } void test_verifier_async_cb_context(void) { RUN(verifier_async_cb_context); } @@ -306,5 +313,6 @@ void test_verifier_value_ptr_arith(void) { run_tests_aux("verifier_value_ptr_arith", verifier_value_ptr_arith__elf_bytes, - init_value_ptr_arith_maps); + init_value_ptr_arith_maps, + true); } diff --git a/tools/testing/selftests/bpf/progs/verifier_ctx.c b/tools/testing/selftests/bpf/progs/verifier_ctx.c index 371780290c0d..c054c8cb7242 100644 --- a/tools/testing/selftests/bpf/progs/verifier_ctx.c +++ b/tools/testing/selftests/bpf/progs/verifier_ctx.c @@ -4,6 +4,10 @@ #include "vmlinux.h" #include #include "bpf_misc.h" +#include "../test_kmods/bpf_testmod_kfunc.h" + +const char ctx_strncmp_target[] = "ctx"; +const char ctx_snprintf_fmt[] = ""; SEC("tc") __description("context stores via BPF_ATOMIC") @@ -69,7 +73,6 @@ __naked void ctx_pointer_to_helper_1(void) SEC("socket") __description("pass modified ctx pointer to helper, 2") __failure __msg("negative offset ctx ptr R1 off=-612 disallowed") -__failure_unpriv __msg_unpriv("negative offset ctx ptr R1 off=-612 disallowed") __naked void ctx_pointer_to_helper_2(void) { asm volatile (" \ @@ -295,77 +298,324 @@ padding_access("sk_reuseport", sk_reuseport_md, hash, 4); SEC("syscall") __description("syscall: write to ctx with fixed offset") __success -__naked void syscall_ctx_fixed_off_write(void) +int syscall_ctx_fixed_off_write(void *ctx) { - asm volatile (" \ - r0 = 0; \ - *(u32*)(r1 + 0) = r0; \ - r1 += 4; \ - *(u32*)(r1 + 0) = r0; \ - exit; \ -" ::: __clobber_all); + char *p = ctx; + + *(__u32 *)p = 0; + *(__u32 *)(p + 4) = 0; + return 0; +} + +SEC("syscall") +__description("syscall: read ctx with fixed offset") +__success +int syscall_ctx_fixed_off_read(void *ctx) +{ + char *p = ctx; + volatile __u32 val; + + val = *(__u32 *)(p + 4); + (void)val; + return 0; +} + +SEC("syscall") +__description("syscall: read ctx with variable offset") +__success +int syscall_ctx_var_off_read(void *ctx) +{ + __u64 off = bpf_get_prandom_u32(); + char *p = ctx; + volatile __u32 val; + + off &= 0xfc; + p += off; + val = *(__u32 *)p; + (void)val; + return 0; +} + +SEC("syscall") +__description("syscall: write ctx with variable offset") +__success +int syscall_ctx_var_off_write(void *ctx) +{ + __u64 off = bpf_get_prandom_u32(); + char *p = ctx; + + off &= 0xfc; + p += off; + *(__u32 *)p = 0; + return 0; +} + +SEC("syscall") +__description("syscall: reject negative variable offset ctx access") +__failure __msg("min value is negative") +int syscall_ctx_neg_var_off(void *ctx) +{ + __u64 off = bpf_get_prandom_u32(); + char *p = ctx; + + off &= 4; + p -= off; + return *(__u32 *)p; +} + +SEC("syscall") +__description("syscall: reject unbounded variable offset ctx access") +__failure __msg("unbounded memory access") +int syscall_ctx_unbounded_var_off(void *ctx) +{ + __u64 off = (__u32)bpf_get_prandom_u32(); + char *p = ctx; + + off <<= 2; + p += off; + return *(__u32 *)p; +} + +SEC("syscall") +__description("syscall: helper read ctx with fixed offset") +__success +int syscall_ctx_helper_fixed_off_read(void *ctx) +{ + char *p = ctx; + + p += 4; + return bpf_strncmp(p, 4, ctx_strncmp_target); +} + +SEC("syscall") +__description("syscall: helper write ctx with fixed offset") +__success +int syscall_ctx_helper_fixed_off_write(void *ctx) +{ + char *p = ctx; + + p += 4; + return bpf_probe_read_kernel(p, 4, 0); +} + +SEC("syscall") +__description("syscall: helper read ctx with variable offset") +__success +int syscall_ctx_helper_var_off_read(void *ctx) +{ + __u64 off = bpf_get_prandom_u32(); + char *p = ctx; + + off &= 0xfc; + p += off; + return bpf_strncmp(p, 4, ctx_strncmp_target); +} + +SEC("syscall") +__description("syscall: helper write ctx with variable offset") +__success +int syscall_ctx_helper_var_off_write(void *ctx) +{ + __u64 off = bpf_get_prandom_u32(); + char *p = ctx; + + off &= 0xfc; + p += off; + return bpf_probe_read_kernel(p, 4, 0); +} + +SEC("syscall") +__description("syscall: helper read zero-sized ctx access") +__success +int syscall_ctx_helper_zero_sized_read(void *ctx) +{ + return bpf_snprintf(0, 0, ctx_snprintf_fmt, ctx, 0); +} + +SEC("syscall") +__description("syscall: helper write zero-sized ctx access") +__success +int syscall_ctx_helper_zero_sized_write(void *ctx) +{ + return bpf_probe_read_kernel(ctx, 0, 0); +} + +SEC("syscall") +__description("syscall: kfunc access ctx with fixed offset") +__success +int syscall_ctx_kfunc_fixed_off(void *ctx) +{ + char *p = ctx; + + p += 4; + bpf_kfunc_call_test_mem_len_pass1(p, 4); + return 0; +} + +SEC("syscall") +__description("syscall: kfunc access ctx with variable offset") +__success +int syscall_ctx_kfunc_var_off(void *ctx) +{ + __u64 off = bpf_get_prandom_u32(); + char *p = ctx; + + off &= 0xfc; + p += off; + bpf_kfunc_call_test_mem_len_pass1(p, 4); + return 0; +} + +SEC("syscall") +__description("syscall: kfunc access zero-sized ctx") +__success +int syscall_ctx_kfunc_zero_sized(void *ctx) +{ + bpf_kfunc_call_test_mem_len_pass1(ctx, 0); + return 0; } /* - * Test that program types without convert_ctx_access can dereference - * their ctx pointer after adding a fixed offset. Variable and negative - * offsets should still be rejected. + * For non-syscall program types without convert_ctx_access, direct ctx + * dereference is still allowed after adding a fixed offset, while variable + * and negative direct accesses reject. + * + * Passing ctx as a helper or kfunc memory argument is only permitted for + * syscall programs, so the helper and kfunc cases below validate rejection + * for non-syscall ctx pointers at fixed, variable, and zero-sized accesses. */ -#define no_rewrite_ctx_access(type, name, off, ld_op) \ +#define no_rewrite_ctx_access(type, name, off, load_t) \ SEC(type) \ __description(type ": read ctx at fixed offset") \ __success \ - __naked void no_rewrite_##name##_fixed(void) \ + int no_rewrite_##name##_fixed(void *ctx) \ { \ - asm volatile (" \ - r1 += %[__off]; \ - r0 = *(" #ld_op " *)(r1 + 0); \ - r0 = 0; \ - exit;" \ - : \ - : __imm_const(__off, off) \ - : __clobber_all); \ + char *p = ctx; \ + volatile load_t val; \ + \ + val = *(load_t *)(p + off); \ + (void)val; \ + return 0; \ } \ SEC(type) \ __description(type ": reject variable offset ctx access") \ __failure __msg("variable ctx access var_off=") \ - __naked void no_rewrite_##name##_var(void) \ + int no_rewrite_##name##_var(void *ctx) \ { \ - asm volatile (" \ - r6 = r1; \ - call %[bpf_get_prandom_u32]; \ - r1 = r6; \ - r0 &= 4; \ - r1 += r0; \ - r0 = *(" #ld_op " *)(r1 + 0); \ - r0 = 0; \ - exit;" \ - : \ - : __imm(bpf_get_prandom_u32) \ - : __clobber_all); \ + __u64 off_var = bpf_get_prandom_u32(); \ + char *p = ctx; \ + \ + off_var &= 4; \ + p += off_var; \ + return *(load_t *)p; \ } \ SEC(type) \ __description(type ": reject negative offset ctx access") \ - __failure __msg("negative offset ctx ptr") \ - __naked void no_rewrite_##name##_neg(void) \ + __failure __msg("invalid bpf_context access") \ + int no_rewrite_##name##_neg(void *ctx) \ { \ - asm volatile (" \ - r1 += %[__neg_off]; \ - r0 = *(" #ld_op " *)(r1 + 0); \ - r0 = 0; \ - exit;" \ - : \ - : __imm_const(__neg_off, -(off)) \ - : __clobber_all); \ + char *p = ctx; \ + \ + p -= 612; \ + return *(load_t *)p; \ + } \ + SEC(type) \ + __description(type ": reject helper read ctx at fixed offset") \ + __failure __msg("dereference of modified ctx ptr") \ + int no_rewrite_##name##_helper_read_fixed(void *ctx) \ + { \ + char *p = ctx; \ + \ + p += off; \ + return bpf_strncmp(p, 4, ctx_strncmp_target); \ + } \ + SEC(type) \ + __description(type ": reject helper write ctx at fixed offset") \ + __failure __msg("dereference of modified ctx ptr") \ + int no_rewrite_##name##_helper_write_fixed(void *ctx) \ + { \ + char *p = ctx; \ + \ + p += off; \ + return bpf_probe_read_kernel(p, 4, 0); \ + } \ + SEC(type) \ + __description(type ": reject helper read ctx with variable offset") \ + __failure __msg("variable ctx access var_off=") \ + int no_rewrite_##name##_helper_read_var(void *ctx) \ + { \ + __u64 off_var = bpf_get_prandom_u32(); \ + char *p = ctx; \ + \ + off_var &= 4; \ + p += off_var; \ + return bpf_strncmp(p, 4, ctx_strncmp_target); \ + } \ + SEC(type) \ + __description(type ": reject helper write ctx with variable offset") \ + __failure __msg("variable ctx access var_off=") \ + int no_rewrite_##name##_helper_write_var(void *ctx) \ + { \ + __u64 off_var = bpf_get_prandom_u32(); \ + char *p = ctx; \ + \ + off_var &= 4; \ + p += off_var; \ + return bpf_probe_read_kernel(p, 4, 0); \ + } \ + SEC(type) \ + __description(type ": reject helper read zero-sized ctx access") \ + __failure __msg("R4 type=ctx expected=fp") \ + int no_rewrite_##name##_helper_read_zero(void *ctx) \ + { \ + return bpf_snprintf(0, 0, ctx_snprintf_fmt, ctx, 0); \ + } \ + SEC(type) \ + __description(type ": reject helper write zero-sized ctx access") \ + __failure __msg("R1 type=ctx expected=fp") \ + int no_rewrite_##name##_helper_write_zero(void *ctx) \ + { \ + return bpf_probe_read_kernel(ctx, 0, 0); \ + } \ + SEC(type) \ + __description(type ": reject kfunc ctx at fixed offset") \ + __failure __msg("dereference of modified ctx ptr") \ + int no_rewrite_##name##_kfunc_fixed(void *ctx) \ + { \ + char *p = ctx; \ + \ + p += off; \ + bpf_kfunc_call_test_mem_len_pass1(p, 4); \ + return 0; \ + } \ + SEC(type) \ + __description(type ": reject kfunc ctx with variable offset") \ + __failure __msg("variable ctx access var_off=") \ + int no_rewrite_##name##_kfunc_var(void *ctx) \ + { \ + __u64 off_var = bpf_get_prandom_u32(); \ + char *p = ctx; \ + \ + off_var &= 4; \ + p += off_var; \ + bpf_kfunc_call_test_mem_len_pass1(p, 4); \ + return 0; \ + } \ + SEC(type) \ + __description(type ": reject kfunc zero-sized ctx access") \ + __failure __msg("R1 type=ctx expected=fp") \ + int no_rewrite_##name##_kfunc_zero(void *ctx) \ + { \ + bpf_kfunc_call_test_mem_len_pass1(ctx, 0); \ + return 0; \ } -no_rewrite_ctx_access("syscall", syscall, 4, u32); -no_rewrite_ctx_access("kprobe", kprobe, 8, u64); -no_rewrite_ctx_access("tracepoint", tp, 8, u64); -no_rewrite_ctx_access("raw_tp", raw_tp, 8, u64); -no_rewrite_ctx_access("raw_tracepoint.w", raw_tp_w, 8, u64); -no_rewrite_ctx_access("fentry/bpf_modify_return_test", fentry, 8, u64); -no_rewrite_ctx_access("cgroup/dev", cgroup_dev, 4, u32); -no_rewrite_ctx_access("netfilter", netfilter, offsetof(struct bpf_nf_ctx, skb), u64); +no_rewrite_ctx_access("kprobe", kprobe, 8, __u64); +no_rewrite_ctx_access("tracepoint", tp, 8, __u64); +no_rewrite_ctx_access("raw_tp", raw_tp, 8, __u64); +no_rewrite_ctx_access("raw_tracepoint.w", raw_tp_w, 8, __u64); +no_rewrite_ctx_access("fentry/bpf_modify_return_test", fentry, 8, __u64); +no_rewrite_ctx_access("cgroup/dev", cgroup_dev, 4, __u32); +no_rewrite_ctx_access("netfilter", netfilter, offsetof(struct bpf_nf_ctx, skb), __u64); char _license[] SEC("license") = "GPL"; diff --git a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c index 94edbd2afa67..f91b484d80f2 100644 --- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c +++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c @@ -716,6 +716,7 @@ BTF_ID_FLAGS(func, bpf_iter_testmod_seq_next, KF_ITER_NEXT | KF_RET_NULL) BTF_ID_FLAGS(func, bpf_iter_testmod_seq_destroy, KF_ITER_DESTROY) BTF_ID_FLAGS(func, bpf_iter_testmod_seq_value) BTF_ID_FLAGS(func, bpf_kfunc_common_test) +BTF_ID_FLAGS(func, bpf_kfunc_call_test_mem_len_pass1) BTF_ID_FLAGS(func, bpf_kfunc_dynptr_test) BTF_ID_FLAGS(func, bpf_kfunc_nested_acquire_nonzero_offset_test, KF_ACQUIRE) BTF_ID_FLAGS(func, bpf_kfunc_nested_acquire_zero_offset_test, KF_ACQUIRE) @@ -1280,7 +1281,6 @@ BTF_ID_FLAGS(func, bpf_kfunc_call_test2) BTF_ID_FLAGS(func, bpf_kfunc_call_test3) BTF_ID_FLAGS(func, bpf_kfunc_call_test4) BTF_ID_FLAGS(func, bpf_kfunc_call_test5) -BTF_ID_FLAGS(func, bpf_kfunc_call_test_mem_len_pass1) BTF_ID_FLAGS(func, bpf_kfunc_call_test_mem_len_fail1) BTF_ID_FLAGS(func, bpf_kfunc_call_test_mem_len_fail2) BTF_ID_FLAGS(func, bpf_kfunc_call_test_acquire, KF_ACQUIRE | KF_RET_NULL) -- 2.52.0