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[176.36.0.241]) by smtp.gmail.com with ESMTPSA id v20-20020a2e5054000000b002c17dcd8d91sm183576ljd.120.2023.11.01.04.05.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 01 Nov 2023 04:05:35 -0700 (PDT) Message-ID: <4ec86365668f6c3b4242232506e896a17aa2af4c.camel@gmail.com> Subject: Re: [PATCH bpf v2 2/2] selftests/bpf: Add test for immediate spilled to stack From: Eduard Zingerman To: Hao Sun , Alexei Starovoitov , Daniel Borkmann , John Fastabend , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Mykola Lysenko , Shuah Khan , Shung-Hsi Yu Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Date: Wed, 01 Nov 2023 13:05:33 +0200 In-Reply-To: <20231101-fix-check-stack-write-v2-2-cb7c17b869b0@gmail.com> References: <20231101-fix-check-stack-write-v2-0-cb7c17b869b0@gmail.com> <20231101-fix-check-stack-write-v2-2-cb7c17b869b0@gmail.com> Autocrypt: addr=eddyz87@gmail.com; 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charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.50.0 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Wed, 2023-11-01 at 08:33 +0100, Hao Sun wrote: > Add a test to check if the verifier correctly reason about the sign > of an immediate spilled to stack by BPF_ST instruction. >=20 > Signed-off-by: Hao Sun > --- > tools/testing/selftests/bpf/verifier/bpf_st_mem.c | 32 +++++++++++++++++= ++++++ > 1 file changed, 32 insertions(+) >=20 > diff --git a/tools/testing/selftests/bpf/verifier/bpf_st_mem.c b/tools/te= sting/selftests/bpf/verifier/bpf_st_mem.c > index 3af2501082b2..0ba23807c46c 100644 > --- a/tools/testing/selftests/bpf/verifier/bpf_st_mem.c > +++ b/tools/testing/selftests/bpf/verifier/bpf_st_mem.c > @@ -65,3 +65,35 @@ > .expected_attach_type =3D BPF_SK_LOOKUP, > .runs =3D -1, > }, > +{ > + "BPF_ST_MEM stack imm sign", > + /* Check if verifier correctly reasons about sign of an > + * immediate spilled to stack by BPF_ST instruction. > + * > + * fp[-8] =3D -44; > + * r0 =3D fp[-8]; > + * if r0 s< 0 goto ret0; > + * r0 =3D -1; > + * exit; > + * ret0: > + * r0 =3D 0; > + * exit; > + */ > + .insns =3D { > + BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, -44), > + BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_10, -8), > + BPF_JMP_IMM(BPF_JSLT, BPF_REG_0, 0, 2), > + BPF_MOV64_IMM(BPF_REG_0, -1), > + BPF_EXIT_INSN(), > + BPF_MOV64_IMM(BPF_REG_0, 0), > + BPF_EXIT_INSN(), > + }, > + /* Use prog type that requires return value in range [0, 1] */ > + .prog_type =3D BPF_PROG_TYPE_SK_LOOKUP, > + .expected_attach_type =3D BPF_SK_LOOKUP, > + .result =3D VERBOSE_ACCEPT, > + .runs =3D -1, > + .errstr =3D "0: (7a) *(u64 *)(r10 -8) =3D -44 ; R10=3Dfp0 fp-8_w= =3D-44\ > + 2: (c5) if r0 s< 0x0 goto pc+2\ > + 2: R0_w=3D-44", > +}, >=20 Please note that this test case fails on CI [0], full log below: 2023-11-01T07:49:51.2841702Z #116/p BPF_ST_MEM stack imm sign FAIL 2023-11-01T07:49:51.2843456Z Unexpected verifier log! 2023-11-01T07:49:51.2844968Z EXP: 2: R0_w=3D-44 2023-11-01T07:49:51.2845583Z RES: 2023-11-01T07:49:51.2846693Z func#0 @0 2023-11-01T07:49:51.2848932Z 0: R1=3Dctx(off=3D0,imm=3D0) R10=3Dfp0 2023-11-01T07:49:51.2853045Z 0: (7a) *(u64 *)(r10 -8) =3D -44 ; R10= =3Dfp0 fp-8_w=3D-44 2023-11-01T07:49:51.2857391Z 1: (79) r0 =3D *(u64 *)(r10 -8) ; R0_w= =3D-44 R10=3Dfp0 fp-8_w=3D-44 2023-11-01T07:49:51.2859127Z 2: (c5) if r0 s< 0x0 goto pc+2 2023-11-01T07:49:51.2862943Z mark_precise: frame0: last_idx 2 first_idx 0 s= ubseq_idx -1=20 2023-11-01T07:49:51.2867511Z mark_precise: frame0: regs=3Dr0 stack=3D befor= e 1: (79) r0 =3D *(u64 *)(r10 -8) 2023-11-01T07:49:51.2872217Z mark_precise: frame0: regs=3D stack=3D-8 befor= e 0: (7a) *(u64 *)(r10 -8) =3D -44 2023-11-01T07:49:51.2872816Z 5: R0_w=3D-44 2023-11-01T07:49:51.2875653Z 5: (b7) r0 =3D 0 ; R0_w= =3D0 2023-11-01T07:49:51.2876493Z 6: (95) exit I suspect that after recent logging fixes instruction number printed after jump changed and that's why test case no longer passes. Note: you can check CI status for submitted patch-sets using link [1]. [0] https://github.com/kernel-patches/bpf/actions/runs/6717053909/job/18254= 330860 [1] https://patchwork.kernel.org/project/netdevbpf/list/