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bpf, selftests: Add verifier test case for jmp32's jeq/jne

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Add a test case to trigger the verifier's incorrect conclusion in the
case of jmp32's jeq/jne. Also here, make use of dead code elimination,
so that we can see the verifier bailing out on unfixed kernels.

Before:

  # ./test_verifier 724
  #724/p jeq32/jne32: bounds checking FAIL
  Failed to load prog 'Permission denied'!
  R4 !read_ok
  verification time 8 usec
  stack depth 0
  processed 8 insns (limit 1000000) max_states_per_insn 0 total_states 1 peak_states 1 mark_read 0
  Summary: 0 PASSED, 0 SKIPPED, 1 FAILED

After:

  # ./test_verifier 724
  #724/p jeq32/jne32: bounds checking OK
  Summary: 1 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220701124727.11153-4-daniel@iogearbox.net
This commit is contained in:
Daniel Borkmann 2022-07-01 14:47:27 +02:00 committed by Andrii Nakryiko
parent 73c4936f91
commit a49b8ce730
1 changed files with 21 additions and 0 deletions
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21
tools/testing/selftests/bpf/verifier/jmp32.c
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@ -864,3 +864,24 @@
.result = ACCEPT,
.flags = F_NEEDS_EFFICIENT_UNALIGNED_ACCESS,
},
{
"jeq32/jne32: bounds checking",
.insns = {
BPF_MOV64_IMM(BPF_REG_6, 563),
BPF_MOV64_IMM(BPF_REG_2, 0),
BPF_ALU64_IMM(BPF_NEG, BPF_REG_2, 0),
BPF_ALU64_IMM(BPF_NEG, BPF_REG_2, 0),
BPF_ALU32_REG(BPF_OR, BPF_REG_2, BPF_REG_6),
BPF_JMP32_IMM(BPF_JNE, BPF_REG_2, 8, 5),
BPF_JMP_IMM(BPF_JSGE, BPF_REG_2, 500, 2),
BPF_MOV64_IMM(BPF_REG_0, 2),
BPF_EXIT_INSN(),
BPF_MOV64_REG(BPF_REG_0, BPF_REG_4),
BPF_EXIT_INSN(),
BPF_MOV64_IMM(BPF_REG_0, 1),
BPF_EXIT_INSN(),
},
.prog_type = BPF_PROG_TYPE_SCHED_CLS,
.result = ACCEPT,
.retval = 1,
},