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| author | Luis Gerhorst <luis.gerhorst@fau.de> | 2026-01-27 12:59:12 +0100 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2026-01-28 18:41:57 -0800 |
| commit | 60d2c438c1bb705cdbf74ce8f12e6e141a4719b0 (patch) | |
| tree | 3e2944caeb45a9e6c70d3f68647df63cfff452ea | |
| parent | cd3b6a3d49f8061d0c4c7e4226783051fe592ae7 (diff) | |
bpf: Test nospec after dead stack write in helper
Without the fix from the previous commit, the selftest fails:
$ ./tools/testing/selftests/bpf/vmtest.sh -- \
./test_progs -t verifier_unpriv
[...]
run_subtest:PASS:obj_open_mem 0 nsec
libbpf: BTF loading error: -EPERM
libbpf: Error loading .BTF into kernel: -EPERM. BTF is optional, ignoring.
libbpf: prog 'unpriv_nospec_after_helper_stack_write': BPF program load failed: -EFAULT
libbpf: prog 'unpriv_nospec_after_helper_stack_write': failed to load: -EFAULT
libbpf: failed to load object 'verifier_unpriv'
run_subtest:FAIL:unexpected_load_failure unexpected error: -14 (errno 14)
VERIFIER LOG:
=============
0: R1=ctx() R10=fp0
0: (b7) r0 = 0 ; R0=P0
1: (55) if r0 != 0x1 goto pc+6 2: R0=Pscalar() R1=ctx() R10=fp0
2: (b7) r2 = 0 ; R2=P0
3: (bf) r3 = r10 ; R3=fp0 R10=fp0
4: (07) r3 += -16 ; R3=fp-16
5: (b7) r4 = 4 ; R4=P4
6: (b7) r5 = 0 ; R5=P0
7: (85) call bpf_skb_load_bytes_relative#68
verifier bug: speculation barrier after jump instruction may not have the desired effect (BPF_CLASS(insn->code) == BPF_JMP || BPF_CLASS(insn->code) == BPF_JMP32)
processed 9 insns (limit 1000000) max_states_per_insn 0 total_states 0 peak_states 0 mark_read 0
=============
[...]
The test is based on the PoC from the report.
Signed-off-by: Luis Gerhorst <luis.gerhorst@fau.de>
Reported-by: Yinhao Hu <dddddd@hust.edu.cn>
Reported-by: Kaiyan Mei <M202472210@hust.edu.cn>
Reported-by: Dongliang Mu <dzm91@hust.edu.cn>
Link: https://lore.kernel.org/bpf/7678017d-b760-4053-a2d8-a6879b0dbeeb@hust.edu.cn/
Link: https://lore.kernel.org/r/20260127115912.3026761-3-luis.gerhorst@fau.de
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
| -rw-r--r-- | tools/testing/selftests/bpf/progs/verifier_unpriv.c | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/tools/testing/selftests/bpf/progs/verifier_unpriv.c b/tools/testing/selftests/bpf/progs/verifier_unpriv.c index 28b4f7035ceb..8ee1243e62a8 100644 --- a/tools/testing/selftests/bpf/progs/verifier_unpriv.c +++ b/tools/testing/selftests/bpf/progs/verifier_unpriv.c @@ -950,4 +950,26 @@ l3_%=: r0 = 0; \ " ::: __clobber_all); } +SEC("socket") +__description("unpriv: nospec after dead stack write in helper") +__success __success_unpriv +__retval(0) +/* Dead code sanitizer rewrites the call to `goto -1`. */ +__naked void unpriv_dead_helper_stack_write_nospec_result(void) +{ + asm volatile (" \ + r0 = 0; \ + if r0 != 1 goto l0_%=; \ + r2 = 0; \ + r3 = r10; \ + r3 += -16; \ + r4 = 4; \ + r5 = 0; \ + call %[bpf_skb_load_bytes_relative]; \ +l0_%=: exit; \ +" : + : __imm(bpf_skb_load_bytes_relative) + : __clobber_all); +} + char _license[] SEC("license") = "GPL"; |