diff options
| -rw-r--r-- | kernel/bpf/verifier.c | 93 |
1 files changed, 89 insertions, 4 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index f35b80c16cda..068f763dcefb 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -20499,13 +20499,46 @@ static int do_misc_fixups(struct bpf_verifier_env *env) /* Convert BPF_CLASS(insn->code) == BPF_ALU64 to 32-bit ALU */ insn->code = BPF_ALU | BPF_OP(insn->code) | BPF_SRC(insn->code); - /* Make divide-by-zero exceptions impossible. */ + /* Make sdiv/smod divide-by-minus-one exceptions impossible. */ + if ((insn->code == (BPF_ALU64 | BPF_MOD | BPF_K) || + insn->code == (BPF_ALU64 | BPF_DIV | BPF_K) || + insn->code == (BPF_ALU | BPF_MOD | BPF_K) || + insn->code == (BPF_ALU | BPF_DIV | BPF_K)) && + insn->off == 1 && insn->imm == -1) { + bool is64 = BPF_CLASS(insn->code) == BPF_ALU64; + bool isdiv = BPF_OP(insn->code) == BPF_DIV; + struct bpf_insn *patchlet; + struct bpf_insn chk_and_sdiv[] = { + BPF_RAW_INSN((is64 ? BPF_ALU64 : BPF_ALU) | + BPF_NEG | BPF_K, insn->dst_reg, + 0, 0, 0), + }; + struct bpf_insn chk_and_smod[] = { + BPF_MOV32_IMM(insn->dst_reg, 0), + }; + + patchlet = isdiv ? chk_and_sdiv : chk_and_smod; + cnt = isdiv ? ARRAY_SIZE(chk_and_sdiv) : ARRAY_SIZE(chk_and_smod); + + new_prog = bpf_patch_insn_data(env, i + delta, patchlet, cnt); + if (!new_prog) + return -ENOMEM; + + delta += cnt - 1; + env->prog = prog = new_prog; + insn = new_prog->insnsi + i + delta; + goto next_insn; + } + + /* Make divide-by-zero and divide-by-minus-one exceptions impossible. */ if (insn->code == (BPF_ALU64 | BPF_MOD | BPF_X) || insn->code == (BPF_ALU64 | BPF_DIV | BPF_X) || insn->code == (BPF_ALU | BPF_MOD | BPF_X) || insn->code == (BPF_ALU | BPF_DIV | BPF_X)) { bool is64 = BPF_CLASS(insn->code) == BPF_ALU64; bool isdiv = BPF_OP(insn->code) == BPF_DIV; + bool is_sdiv = isdiv && insn->off == 1; + bool is_smod = !isdiv && insn->off == 1; struct bpf_insn *patchlet; struct bpf_insn chk_and_div[] = { /* [R,W]x div 0 -> 0 */ @@ -20525,10 +20558,62 @@ static int do_misc_fixups(struct bpf_verifier_env *env) BPF_JMP_IMM(BPF_JA, 0, 0, 1), BPF_MOV32_REG(insn->dst_reg, insn->dst_reg), }; + struct bpf_insn chk_and_sdiv[] = { + /* [R,W]x sdiv 0 -> 0 + * LLONG_MIN sdiv -1 -> LLONG_MIN + * INT_MIN sdiv -1 -> INT_MIN + */ + BPF_MOV64_REG(BPF_REG_AX, insn->src_reg), + BPF_RAW_INSN((is64 ? BPF_ALU64 : BPF_ALU) | + BPF_ADD | BPF_K, BPF_REG_AX, + 0, 0, 1), + BPF_RAW_INSN((is64 ? BPF_JMP : BPF_JMP32) | + BPF_JGT | BPF_K, BPF_REG_AX, + 0, 4, 1), + BPF_RAW_INSN((is64 ? BPF_JMP : BPF_JMP32) | + BPF_JEQ | BPF_K, BPF_REG_AX, + 0, 1, 0), + BPF_RAW_INSN((is64 ? BPF_ALU64 : BPF_ALU) | + BPF_MOV | BPF_K, insn->dst_reg, + 0, 0, 0), + /* BPF_NEG(LLONG_MIN) == -LLONG_MIN == LLONG_MIN */ + BPF_RAW_INSN((is64 ? BPF_ALU64 : BPF_ALU) | + BPF_NEG | BPF_K, insn->dst_reg, + 0, 0, 0), + BPF_JMP_IMM(BPF_JA, 0, 0, 1), + *insn, + }; + struct bpf_insn chk_and_smod[] = { + /* [R,W]x mod 0 -> [R,W]x */ + /* [R,W]x mod -1 -> 0 */ + BPF_MOV64_REG(BPF_REG_AX, insn->src_reg), + BPF_RAW_INSN((is64 ? BPF_ALU64 : BPF_ALU) | + BPF_ADD | BPF_K, BPF_REG_AX, + 0, 0, 1), + BPF_RAW_INSN((is64 ? BPF_JMP : BPF_JMP32) | + BPF_JGT | BPF_K, BPF_REG_AX, + 0, 3, 1), + BPF_RAW_INSN((is64 ? BPF_JMP : BPF_JMP32) | + BPF_JEQ | BPF_K, BPF_REG_AX, + 0, 3 + (is64 ? 0 : 1), 1), + BPF_MOV32_IMM(insn->dst_reg, 0), + BPF_JMP_IMM(BPF_JA, 0, 0, 1), + *insn, + BPF_JMP_IMM(BPF_JA, 0, 0, 1), + BPF_MOV32_REG(insn->dst_reg, insn->dst_reg), + }; - patchlet = isdiv ? chk_and_div : chk_and_mod; - cnt = isdiv ? ARRAY_SIZE(chk_and_div) : - ARRAY_SIZE(chk_and_mod) - (is64 ? 2 : 0); + if (is_sdiv) { + patchlet = chk_and_sdiv; + cnt = ARRAY_SIZE(chk_and_sdiv); + } else if (is_smod) { + patchlet = chk_and_smod; + cnt = ARRAY_SIZE(chk_and_smod) - (is64 ? 2 : 0); + } else { + patchlet = isdiv ? chk_and_div : chk_and_mod; + cnt = isdiv ? ARRAY_SIZE(chk_and_div) : + ARRAY_SIZE(chk_and_mod) - (is64 ? 2 : 0); + } new_prog = bpf_patch_insn_data(env, i + delta, patchlet, cnt); if (!new_prog) |