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Wed, 03 Jun 2026 08:47:29 -0700 (PDT) Received: from localhost ([2001:569:58a0:da00:a5c8:c4ce:f7c1:40c1]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2c164f84335sm29666995ad.19.2026.06.03.08.47.28 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 03 Jun 2026 08:47:28 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Wed, 03 Jun 2026 11:47:27 -0400 Message-Id: Cc: , , Subject: Re: [PATCH bpf-next] selftests/bpf: Add arena direct-value one-past-end reject test From: "Emil Tsalapatis" To: "Woojin Ji" , "Andrii Nakryiko" , "Eduard Zingerman" , "Alexei Starovoitov" , "Daniel Borkmann" , "Martin KaFai Lau" , "Kumar Kartikeya Dwivedi" , "Song Liu" , "Yonghong Song" , "Jiri Olsa" , "Shuah Khan" X-Mailer: aerc 0.21.0-0-g5549850facc2 References: <20260603-arena-direct-value-v1-v1-1-7b31cc0a8cac@gmail.com> In-Reply-To: <20260603-arena-direct-value-v1-v1-1-7b31cc0a8cac@gmail.com> On Wed Jun 3, 2026 at 8:09 AM EDT, Woojin Ji wrote: > BPF_MAP_TYPE_ARENA supports direct-value pseudo loads, but unlike array > maps its map value_size is zero and the valid direct-value range is the > arena mmap size, max_entries * PAGE_SIZE. > > Commit 3ac1a467e376 ("bpf: Fix off-by-one boundary validation in arena > direct-value access") fixed arena_map_direct_value_addr() to reject an > offset exactly at the end of the arena mapping. Add a regression test > that loads a BPF_PSEUDO_MAP_VALUE with off =3D=3D arena_size and verifies > that the verifier rejects it with the expected offset in the log. > > Unlike __arena global relocation, where insn[1].imm depends on > compiler/layout, this raw instruction directly drives > map_direct_value_addr(map, &addr, off) with off =3D=3D arena_size, so the > boundary check is exercised directly. > > Assisted-by: ChatGPT:gpt-5.5 > Signed-off-by: Woojin Ji > --- Makes sense to add this, but I don't see why this isn't a single test program in verifier_arena.c and requires a whole new userspace test. > Tested with a reduced test_progs runner because the local source/output > combination has unrelated build failures in progs/bpf_cubic.c and > test_kmods/bpf_testmod.ko, so the stock full test_progs binary is not > produced. > > Before fix, on host Arch kernel 7.0.10-arch1-1: > arena_direct_value/one_past_end: FAIL, prog_load returned fd 5 > > After fix, on QEMU guest 7.1.0-rc6-00063-gba3e43a9e601: > #1/1 arena_direct_value/one_past_end:OK > #1 arena_direct_value:OK > Summary: 1/1 PASSED, 0 SKIPPED, 0 FAILED > --- > .../selftests/bpf/prog_tests/arena_direct_value.c | 73 ++++++++++++++++= ++++++ > 1 file changed, 73 insertions(+) > > diff --git a/tools/testing/selftests/bpf/prog_tests/arena_direct_value.c = b/tools/testing/selftests/bpf/prog_tests/arena_direct_value.c > new file mode 100644 > index 000000000000..b7760b021670 > --- /dev/null > +++ b/tools/testing/selftests/bpf/prog_tests/arena_direct_value.c > @@ -0,0 +1,73 @@ > +// SPDX-License-Identifier: GPL-2.0 > + > +#include > +#include > +#include > +#include > +#include > + > +#define ARENA_PAGES 32 > + > +static void test_arena_direct_value_one_past_end(void) > +{ > + char log_buf[16384] =3D {}, expected[128]; > + __u32 arena_sz =3D ARENA_PAGES * getpagesize(); > + struct bpf_insn insns[] =3D { > + BPF_LD_IMM64_RAW(BPF_REG_1, BPF_PSEUDO_MAP_VALUE, 0), > + BPF_MOV64_IMM(BPF_REG_0, 0), > + BPF_EXIT_INSN(), > + }; > + LIBBPF_OPTS(bpf_map_create_opts, map_opts); > + LIBBPF_OPTS(bpf_prog_load_opts, prog_opts); > + void *arena =3D MAP_FAILED; > + int map_fd, prog_fd; > + > + map_opts.map_flags =3D BPF_F_MMAPABLE; > + prog_opts.log_buf =3D log_buf; > + prog_opts.log_size =3D sizeof(log_buf); > + prog_opts.log_level =3D 1; > + > + map_fd =3D bpf_map_create(BPF_MAP_TYPE_ARENA, "arena_direct_value", > + 0, 0, ARENA_PAGES, &map_opts); > + if (map_fd < 0) { > + if (errno =3D=3D EOPNOTSUPP || errno =3D=3D EINVAL) { > + test__skip(); > + return; > + } > + ASSERT_GE(map_fd, 0, "bpf_map_create"); > + return; > + } > + > + arena =3D mmap(NULL, arena_sz, PROT_READ | PROT_WRITE, MAP_SHARED, map_= fd, 0); > + if (!ASSERT_NEQ(arena, MAP_FAILED, "arena_mmap")) > + goto cleanup; > + > + insns[0].imm =3D map_fd; > + insns[1].imm =3D arena_sz; > + > + prog_fd =3D bpf_prog_load(BPF_PROG_TYPE_RAW_TRACEPOINT, > + "arena_direct_value", "GPL", insns, > + ARRAY_SIZE(insns), &prog_opts); > + if (!ASSERT_LT(prog_fd, 0, "prog_load")) { > + if (prog_fd >=3D 0) > + close(prog_fd); > + prog_fd =3D -1; > + goto cleanup; > + } > + > + snprintf(expected, sizeof(expected), > + "invalid access to map value pointer, value_size=3D0 off=3D%u", > + arena_sz); > + ASSERT_HAS_SUBSTR(log_buf, expected, "verifier_log"); > + > +cleanup: > + if (arena !=3D MAP_FAILED) > + munmap(arena, arena_sz); > + close(map_fd); > +} > + > +void test_arena_direct_value(void) > +{ > + if (test__start_subtest("one_past_end")) > + test_arena_direct_value_one_past_end(); > +} > > --- > base-commit: ba3e43a9e601636f5edb54e259a74f96ca3b8fd8 > change-id: 20260603-arena-direct-value-v1-ef4df857b98b > > Best regards, > -- =20 > Woojin Ji