On Wed, Nov 1, 2023 at 12:05 PM Eduard Zingerman eddyz87@gmail.com wrote:
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.
Signed-off-by: Hao Sun sunhao.th@gmail.com
tools/testing/selftests/bpf/verifier/bpf_st_mem.c | 32 +++++++++++++++++++++++ 1 file changed, 32 insertions(+)
diff --git a/tools/testing/selftests/bpf/verifier/bpf_st_mem.c b/tools/testing/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 = BPF_SK_LOOKUP, .runs = -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] = -44;* r0 = fp[-8];* if r0 s< 0 goto ret0;* r0 = -1;* exit;* ret0:* r0 = 0;* exit;*/.insns = {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 = BPF_PROG_TYPE_SK_LOOKUP,.expected_attach_type = BPF_SK_LOOKUP,.result = VERBOSE_ACCEPT,.runs = -1,.errstr = "0: (7a) *(u64 *)(r10 -8) = -44 ; R10=fp0 fp-8_w=-44\2: (c5) if r0 s< 0x0 goto pc+2\2: R0_w=-44",+},
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=-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=ctx(off=0,imm=0) R10=fp0 2023-11-01T07:49:51.2853045Z 0: (7a) *(u64 *)(r10 -8) = -44 ; R10=fp0 fp-8_w=-44 2023-11-01T07:49:51.2857391Z 1: (79) r0 = *(u64 *)(r10 -8) ; R0_w=-44 R10=fp0 fp-8_w=-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 subseq_idx -1 2023-11-01T07:49:51.2867511Z mark_precise: frame0: regs=r0 stack= before 1: (79) r0 = *(u64 *)(r10 -8) 2023-11-01T07:49:51.2872217Z mark_precise: frame0: regs= stack=-8 before 0: (7a) *(u64 *)(r10 -8) = -44 2023-11-01T07:49:51.2872816Z 5: R0_w=-44 2023-11-01T07:49:51.2875653Z 5: (b7) r0 = 0 ; R0_w=0 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.
Yes, so I guess we can just drop the line number there, will send patch v3.
Note: you can check CI status for submitted patch-sets using link [1].
[0] https://github.com/kernel-patches/bpf/actions/runs/6717053909/job/1825433086... [1] https://patchwork.kernel.org/project/netdevbpf/list/
Thanks.