From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from 66-220-144-178.mail-mxout.facebook.com (66-220-144-178.mail-mxout.facebook.com [66.220.144.178]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 78BC5349AE0 for ; Fri, 17 Apr 2026 03:48:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=66.220.144.178 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776397728; cv=none; b=lRyedJaPff97F2404/XN9uof0JJ4j7fM6Sz6yHGAobf20yDIOEL69gCAstMTyCwZbpQfbfl7Awhh1SNLPm5h8LQFkqIKez8rsvh0NSwPtnN+I1z6n+DKh5GBXPOATBj4PbCebNy5Ck+kio1SSOHGIQmfz0xJcBthxdyELJ2HBxo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776397728; c=relaxed/simple; bh=m2oWzX0WHrOu7/k4zHjs4v4oSNSzIXDTmFGkGA73gr4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=ud1oKYEz0nCcJ+BZmzgGH8Ck6rvnyWolNSWJxI4wRMu+nEnv0fM7Wn8fs96sFOx5uiZoPeEEF0A21f3FdfL2k3K9H7FYWNqHFTwoe36Ci4A4D2kVDigiDLN+gnq6Icd2FAiWdJLRKD/jZRw4+HLhoPso31/no6cGoFhq7IQUeuI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.dev; spf=fail smtp.mailfrom=linux.dev; arc=none smtp.client-ip=66.220.144.178 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=linux.dev Received: by devvm16039.vll0.facebook.com (Postfix, from userid 128203) id 7FB73403C25A2; Thu, 16 Apr 2026 20:48:38 -0700 (PDT) From: Yonghong Song To: bpf@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , "Jose E . Marchesi" , kernel-team@fb.com, Martin KaFai Lau Subject: [PATCH bpf-next v5 16/16] selftests/bpf: Add verifier tests for stack argument validation Date: Thu, 16 Apr 2026 20:48:38 -0700 Message-ID: <20260417034838.2638137-1-yonghong.song@linux.dev> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260417034658.2625353-1-yonghong.song@linux.dev> References: <20260417034658.2625353-1-yonghong.song@linux.dev> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Add inline-asm based verifier tests that exercise stack argument validation logic directly. Positive tests: - subprog call with 6 arg's - Two sequential calls to different subprogs (6-arg and 7-arg) - Share a r11 store for both branches - Sequential calls reuse stack arg's Negative tests =E2=80=94 verifier rejection: - Read from uninitialized incoming stack arg slot - Gap in outgoing slots: only r11-16 written, r11-8 missing - Sub-8-byte stack arg write (4 bytes instead of 8) - Write at r11-80, exceeding max 7 stack args - Missing store on one branch with a shared store Negative tests =E2=80=94 pointer/ref tracking: - Pruning type mismatch: one branch stores PTR_TO_STACK, the other stores a scalar, callee dereferences =E2=80=94 must not prune - Release invalidation: bpf_sk_release invalidates a socket pointer stored in a stack arg slot - Packet pointer invalidation: bpf_skb_pull_data invalidates a packet pointer stored in a stack arg slot - Null propagation: PTR_TO_MAP_VALUE_OR_NULL stored in stack arg slot, null branch attempts dereference via callee Signed-off-by: Yonghong Song --- .../selftests/bpf/prog_tests/verifier.c | 2 + .../selftests/bpf/progs/verifier_stack_arg.c | 463 ++++++++++++++++++ 2 files changed, 465 insertions(+) create mode 100644 tools/testing/selftests/bpf/progs/verifier_stack_arg.= c diff --git a/tools/testing/selftests/bpf/prog_tests/verifier.c b/tools/te= sting/selftests/bpf/prog_tests/verifier.c index a96b25ebff23..aef21cf2987b 100644 --- a/tools/testing/selftests/bpf/prog_tests/verifier.c +++ b/tools/testing/selftests/bpf/prog_tests/verifier.c @@ -91,6 +91,7 @@ #include "verifier_sockmap_mutate.skel.h" #include "verifier_spill_fill.skel.h" #include "verifier_spin_lock.skel.h" +#include "verifier_stack_arg.skel.h" #include "verifier_stack_ptr.skel.h" #include "verifier_store_release.skel.h" #include "verifier_subprog_precision.skel.h" @@ -238,6 +239,7 @@ void test_verifier_sock_addr(void) { RUN(v= erifier_sock_addr); } void test_verifier_sockmap_mutate(void) { RUN(verifier_sockmap_mut= ate); } void test_verifier_spill_fill(void) { RUN(verifier_spill_fill)= ; } void test_verifier_spin_lock(void) { RUN(verifier_spin_lock);= } +void test_verifier_stack_arg(void) { RUN(verifier_stack_arg);= } void test_verifier_stack_ptr(void) { RUN(verifier_stack_ptr);= } void test_verifier_store_release(void) { RUN(verifier_store_relea= se); } void test_verifier_subprog_precision(void) { RUN(verifier_subprog_pre= cision); } diff --git a/tools/testing/selftests/bpf/progs/verifier_stack_arg.c b/too= ls/testing/selftests/bpf/progs/verifier_stack_arg.c new file mode 100644 index 000000000000..d212b6c3cac7 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/verifier_stack_arg.c @@ -0,0 +1,463 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2026 Meta Platforms, Inc. and affiliates. */ + +#include +#include +#include "bpf_misc.h" + +struct { + __uint(type, BPF_MAP_TYPE_HASH); + __uint(max_entries, 1); + __type(key, long long); + __type(value, long long); +} map_hash_8b SEC(".maps"); + +#if defined(__TARGET_ARCH_x86) && defined(__BPF_FEATURE_STACK_ARGUMENT) + +__noinline __used +static int subprog_6args(int a, int b, int c, int d, int e, int f) +{ + return a + b + c + d + e + f; +} + +__noinline __used +static int subprog_7args(int a, int b, int c, int d, int e, int f, int g= ) +{ + return a + b + c + d + e + f + g; +} + +__noinline __used +static int subprog_8args(int a, int b, int c, int d, int e, int f, int g= , int h) +{ + return a + b + c + d + e + f + g + h; +} + +__noinline __used +static long subprog_deref_arg6(long a, long b, long c, long d, long e, l= ong *f) +{ + return *f; +} + +SEC("tc") +__description("stack_arg: subprog with 6 args") +__success +__arch_x86_64 +__naked void stack_arg_6args(void) +{ + asm volatile ( + "r1 =3D 1;" + "r2 =3D 2;" + "r3 =3D 3;" + "r4 =3D 4;" + "r5 =3D 5;" + "*(u64 *)(r11 - 8) =3D 6;" + "call subprog_6args;" + "exit;" + ::: __clobber_all + ); +} + +SEC("tc") +__description("stack_arg: two subprogs with >5 args") +__success +__arch_x86_64 +__naked void stack_arg_two_subprogs(void) +{ + asm volatile ( + "r1 =3D 1;" + "r2 =3D 2;" + "r3 =3D 3;" + "r4 =3D 4;" + "r5 =3D 5;" + "*(u64 *)(r11 - 8) =3D 10;" + "call subprog_6args;" + "r6 =3D r0;" + "r1 =3D 1;" + "r2 =3D 2;" + "r3 =3D 3;" + "r4 =3D 4;" + "r5 =3D 5;" + "*(u64 *)(r11 - 16) =3D 30;" + "*(u64 *)(r11 - 8) =3D 20;" + "call subprog_7args;" + "r0 +=3D r6;" + "exit;" + ::: __clobber_all + ); +} + +SEC("tc") +__description("stack_arg: read from uninitialized stack arg slot") +__failure +__arch_x86_64 +__msg("invalid read from stack arg") +__naked void stack_arg_read_uninitialized(void) +{ + asm volatile ( + "r0 =3D *(u64 *)(r11 + 8);" + "r0 =3D 0;" + "exit;" + ::: __clobber_all + ); +} + +SEC("tc") +__description("stack_arg: gap at offset -8, only wrote -16") +__failure +__arch_x86_64 +__msg("stack arg#6 not properly initialized") +__naked void stack_arg_gap_at_minus8(void) +{ + asm volatile ( + "r1 =3D 1;" + "r2 =3D 2;" + "r3 =3D 3;" + "r4 =3D 4;" + "r5 =3D 5;" + "*(u64 *)(r11 - 16) =3D 30;" + "call subprog_7args;" + "exit;" + ::: __clobber_all + ); +} + +SEC("tc") +__description("stack_arg: incorrect size of stack arg write") +__failure +__arch_x86_64 +__msg("stack arg write must be 8 bytes, got 4") +__naked void stack_arg_not_written(void) +{ + asm volatile ( + "r1 =3D 1;" + "r2 =3D 2;" + "r3 =3D 3;" + "r4 =3D 4;" + "r5 =3D 5;" + "*(u32 *)(r11 - 8) =3D 30;" + "call subprog_6args;" + "exit;" + ::: __clobber_all + ); +} + +SEC("tc") +__description("stack_arg: pruning with different stack arg types") +__failure +__flag(BPF_F_TEST_STATE_FREQ) +__arch_x86_64 +__msg("R1 invalid mem access") +__naked void stack_arg_pruning_type_mismatch(void) +{ + asm volatile ( + "call %[bpf_get_prandom_u32];" + "r6 =3D r0;" + /* local =3D 0 on program stack */ + "r7 =3D 0;" + "*(u64 *)(r10 - 8) =3D r7;" + /* Branch based on random value */ + "if r6 s> 3 goto l0_%=3D;" + /* Path 1: store stack pointer to outgoing arg6 */ + "r1 =3D r10;" + "r1 +=3D -8;" + "*(u64 *)(r11 - 8) =3D r1;" + "goto l1_%=3D;" + "l0_%=3D:" + /* Path 2: store scalar to outgoing arg6 */ + "*(u64 *)(r11 - 8) =3D 42;" + "l1_%=3D:" + /* Call subprog that dereferences arg6 */ + "r1 =3D r6;" + "r2 =3D 0;" + "r3 =3D 0;" + "r4 =3D 0;" + "r5 =3D 0;" + "call subprog_deref_arg6;" + "exit;" + :: __imm(bpf_get_prandom_u32) + : __clobber_all + ); +} + +SEC("tc") +__description("stack_arg: release_reference invalidates stack arg slot") +__failure +__arch_x86_64 +__msg("R1 invalid sock access") +__naked void stack_arg_release_ref(void) +{ + asm volatile ( + "r6 =3D r1;" + /* struct bpf_sock_tuple tuple =3D {} */ + "r2 =3D 0;" + "*(u32 *)(r10 - 8) =3D r2;" + "*(u64 *)(r10 - 16) =3D r2;" + "*(u64 *)(r10 - 24) =3D r2;" + "*(u64 *)(r10 - 32) =3D r2;" + "*(u64 *)(r10 - 40) =3D r2;" + "*(u64 *)(r10 - 48) =3D r2;" + /* sk =3D bpf_sk_lookup_tcp(ctx, &tuple, sizeof(tuple), 0, 0) */ + "r1 =3D r6;" + "r2 =3D r10;" + "r2 +=3D -48;" + "r3 =3D %[sizeof_bpf_sock_tuple];" + "r4 =3D 0;" + "r5 =3D 0;" + "call %[bpf_sk_lookup_tcp];" + /* r0 =3D sk (PTR_TO_SOCK_OR_NULL) */ + "if r0 =3D=3D 0 goto l0_%=3D;" + /* Store sock ref to outgoing arg6 slot */ + "*(u64 *)(r11 - 8) =3D r0;" + /* Release the reference =E2=80=94 invalidates the stack arg slot */ + "r1 =3D r0;" + "call %[bpf_sk_release];" + /* Call subprog that dereferences arg6 =E2=80=94 should fail */ + "r1 =3D 1;" + "r2 =3D 2;" + "r3 =3D 3;" + "r4 =3D 4;" + "r5 =3D 5;" + "call subprog_deref_arg6;" + "l0_%=3D:" + "r0 =3D 0;" + "exit;" + : + : __imm(bpf_sk_lookup_tcp), + __imm(bpf_sk_release), + __imm_const(sizeof_bpf_sock_tuple, sizeof(struct bpf_sock_tuple)) + : __clobber_all + ); +} + +SEC("tc") +__description("stack_arg: pkt pointer in stack arg slot invalidated afte= r pull_data") +__failure +__arch_x86_64 +__msg("invalid access to packet") +__naked void stack_arg_stale_pkt_ptr(void) +{ + asm volatile ( + "r6 =3D r1;" + "r7 =3D *(u32 *)(r6 + %[__sk_buff_data]);" + "r8 =3D *(u32 *)(r6 + %[__sk_buff_data_end]);" + /* check pkt has at least 1 byte */ + "r0 =3D r7;" + "r0 +=3D 1;" + "if r0 > r8 goto l0_%=3D;" + /* Store valid pkt pointer to outgoing arg6 slot */ + "*(u64 *)(r11 - 8) =3D r7;" + /* bpf_skb_pull_data invalidates all pkt pointers */ + "r1 =3D r6;" + "r2 =3D 0;" + "call %[bpf_skb_pull_data];" + /* Call subprog that dereferences arg6 =E2=80=94 should fail */ + "r1 =3D 1;" + "r2 =3D 2;" + "r3 =3D 3;" + "r4 =3D 4;" + "r5 =3D 5;" + "call subprog_deref_arg6;" + "l0_%=3D:" + "r0 =3D 0;" + "exit;" + : + : __imm(bpf_skb_pull_data), + __imm_const(__sk_buff_data, offsetof(struct __sk_buff, data)), + __imm_const(__sk_buff_data_end, offsetof(struct __sk_buff, data_end)= ) + : __clobber_all + ); +} + +SEC("tc") +__description("stack_arg: null propagation rejects deref on null branch"= ) +__failure +__arch_x86_64 +__msg("R1 invalid mem access") +__naked void stack_arg_null_propagation_fail(void) +{ + asm volatile ( + "r1 =3D 0;" + "*(u64 *)(r10 - 8) =3D r1;" + /* r0 =3D bpf_map_lookup_elem(&map_hash_8b, &key) */ + "r2 =3D r10;" + "r2 +=3D -8;" + "r1 =3D %[map_hash_8b] ll;" + "call %[bpf_map_lookup_elem];" + /* Store PTR_TO_MAP_VALUE_OR_NULL to outgoing arg6 slot */ + "*(u64 *)(r11 - 8) =3D r0;" + /* null check on r0 */ + "if r0 !=3D 0 goto l0_%=3D;" + /* + * On null branch, outgoing slot is SCALAR(0). + * Call subprog that dereferences arg6 =E2=80=94 should fail. + */ + "r1 =3D 0;" + "r2 =3D 0;" + "r3 =3D 0;" + "r4 =3D 0;" + "r5 =3D 0;" + "call subprog_deref_arg6;" + "l0_%=3D:" + "r0 =3D 0;" + "exit;" + : + : __imm(bpf_map_lookup_elem), + __imm_addr(map_hash_8b) + : __clobber_all + ); +} + +SEC("tc") +__description("stack_arg: missing store on one branch") +__failure +__arch_x86_64 +__msg("stack arg#6 not properly initialized") +__naked void stack_arg_missing_store_one_branch(void) +{ + asm volatile ( + "r1 =3D 1;" + "r2 =3D 2;" + "r3 =3D 3;" + "r4 =3D 4;" + "r5 =3D 5;" + /* Write arg7 (r11-16) before branch */ + "*(u64 *)(r11 - 16) =3D 20;" + "call %[bpf_get_prandom_u32];" + "if r0 > 0 goto l0_%=3D;" + /* Path 1: write arg6 and call */ + "*(u64 *)(r11 - 8) =3D 10;" + "r1 =3D 1;" + "r2 =3D 2;" + "r3 =3D 3;" + "r4 =3D 4;" + "r5 =3D 5;" + "call subprog_7args;" + "goto l1_%=3D;" + "l0_%=3D:" + /* Path 2: missing arg6 store, call should fail */ + "r1 =3D 1;" + "r2 =3D 2;" + "r3 =3D 3;" + "r4 =3D 4;" + "r5 =3D 5;" + "call subprog_7args;" + "l1_%=3D:" + "r0 =3D 0;" + "exit;" + :: __imm(bpf_get_prandom_u32) + : __clobber_all + ); +} + +SEC("tc") +__description("stack_arg: share a store for both branches") +__success __retval(0) +__arch_x86_64 +__naked void stack_arg_shared_store(void) +{ + asm volatile ( + "r1 =3D 1;" + "r2 =3D 2;" + "r3 =3D 3;" + "r4 =3D 4;" + "r5 =3D 5;" + /* Write arg7 (r11-16) before branch */ + "*(u64 *)(r11 - 16) =3D 20;" + "call %[bpf_get_prandom_u32];" + "if r0 > 0 goto l0_%=3D;" + /* Path 1: write arg6 and call */ + "*(u64 *)(r11 - 8) =3D 10;" + "r1 =3D 1;" + "r2 =3D 2;" + "r3 =3D 3;" + "r4 =3D 4;" + "r5 =3D 5;" + "call subprog_7args;" + "goto l1_%=3D;" + "l0_%=3D:" + /* Path 2: also write arg6 and call */ + "*(u64 *)(r11 - 8) =3D 30;" + "r1 =3D 1;" + "r2 =3D 2;" + "r3 =3D 3;" + "r4 =3D 4;" + "r5 =3D 5;" + "call subprog_7args;" + "l1_%=3D:" + "r0 =3D 0;" + "exit;" + :: __imm(bpf_get_prandom_u32) + : __clobber_all + ); +} + +SEC("tc") +__description("stack_arg: write beyond max outgoing depth") +__failure +__arch_x86_64 +__msg("stack arg write offset -80 exceeds max 7 stack args") +__naked void stack_arg_write_beyond_max(void) +{ + asm volatile ( + "r1 =3D 1;" + "r2 =3D 2;" + "r3 =3D 3;" + "r4 =3D 4;" + "r5 =3D 5;" + /* Write to offset -80, way beyond any callee's needs */ + "*(u64 *)(r11 - 80) =3D 99;" + "*(u64 *)(r11 - 16) =3D 20;" + "*(u64 *)(r11 - 8) =3D 10;" + "call subprog_7args;" + "r0 =3D 0;" + "exit;" + ::: __clobber_all + ); +} + +SEC("tc") +__description("stack_arg: sequential calls reuse slots") +__success __retval(56) +__arch_x86_64 +__naked void stack_arg_sequential_calls(void) +{ + asm volatile ( + /* call1: subprog_7args(1,2,3,4,5,6,7) =3D 28 */ + "r1 =3D 1;" + "r2 =3D 2;" + "r3 =3D 3;" + "r4 =3D 4;" + "r5 =3D 5;" + "*(u64 *)(r11 - 8) =3D 6;" + "*(u64 *)(r11 - 16) =3D 7;" + "call subprog_7args;" + "r6 =3D r0;" + /* call2: reuse stack arg slots from call1, + * subprog_7args(1,2,3,4,5,6,7) =3D 28 + */ + "r1 =3D 1;" + "r2 =3D 2;" + "r3 =3D 3;" + "r4 =3D 4;" + "r5 =3D 5;" + "call subprog_7args;" + /* total: 28 + 28 =3D 56 */ + "r0 +=3D r6;" + "exit;" + ::: __clobber_all + ); +} + +#else + +SEC("socket") +__description("stack_arg is not supported by compiler or jit, use a dumm= y test") +__success +int dummy_test(void) +{ + return 0; +} + +#endif + +char _license[] SEC("license") =3D "GPL"; --=20 2.52.0