Messages in this thread | | | From | Jann Horn <> | Date | Mon, 4 Dec 2017 21:26:03 +0100 | Subject | Re: BPF: bug without effect in BPF_RSH case of adjust_scalar_min_max_vals() |
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On Mon, Dec 4, 2017 at 6:03 PM, Jann Horn <jannh@google.com> wrote: > As far as I can tell, commit b03c9f9fdc37 ("bpf/verifier: track signed > and unsigned min/max values") introduced the following effectless bug > in the BPF_RSH case of adjust_scalar_min_max_vals() (unless that's > intentional): [...] > ======================= > BPF_LD_MAP_FD(BPF_REG_ARG1, mapfd), > > BPF_MOV64_REG(BPF_REG_TMP, BPF_REG_FP), > BPF_ALU64_IMM(BPF_ADD, BPF_REG_TMP, -4), // allocate 4 bytes stack > BPF_MOV32_IMM(BPF_REG_ARG2, 1), > BPF_STX_MEM(BPF_W, BPF_REG_TMP, BPF_REG_ARG2, 0), > BPF_MOV64_REG(BPF_REG_ARG2, BPF_REG_TMP), > BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem), > BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 2), > BPF_MOV64_REG(BPF_REG_0, 0), // prepare exit > BPF_EXIT_INSN(), // exit > BPF_LDX_MEM(BPF_W, BPF_REG_3, BPF_REG_0, 0), > > BPF_ALU64_IMM(BPF_AND, BPF_REG_3, 0xf), > BPF_MOV64_IMM(BPF_REG_1, -42), > BPF_ALU64_REG(BPF_ADD, BPF_REG_1, BPF_REG_3), > BPF_MOV64_IMM(BPF_REG_2, 2), > BPF_ALU64_REG(BPF_RSH, BPF_REG_1, BPF_REG_2), > BPF_EXIT_INSN() > =======================
For using the eBPF bytecode in selftests:
Signed-off-by: Jann Horn <jannh@google.com>
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