diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 48c2705db22cbbd1e6efc6334b077fcb2711b875..90493a66dddd397c5354cb0ac8ce157dafae212d 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -1637,21 +1637,42 @@ static int check_alu_op(struct verifier_env *env, struct bpf_insn *insn) return 0; } -static void find_good_pkt_pointers(struct verifier_env *env, - struct reg_state *dst_reg) +static void find_good_pkt_pointers(struct verifier_state *state, + const struct reg_state *dst_reg) { - struct verifier_state *state = &env->cur_state; struct reg_state *regs = state->regs, *reg; int i; - /* r2 = r3; - * r2 += 8 - * if (r2 > pkt_end) goto somewhere - * r2 == dst_reg, pkt_end == src_reg, - * r2=pkt(id=n,off=8,r=0) - * r3=pkt(id=n,off=0,r=0) - * find register r3 and mark its range as r3=pkt(id=n,off=0,r=8) - * so that range of bytes [r3, r3 + 8) is safe to access + + /* LLVM can generate two kind of checks: + * + * Type 1: + * + * r2 = r3; + * r2 += 8; + * if (r2 > pkt_end) goto + * + * + * Where: + * r2 == dst_reg, pkt_end == src_reg + * r2=pkt(id=n,off=8,r=0) + * r3=pkt(id=n,off=0,r=0) + * + * Type 2: + * + * r2 = r3; + * r2 += 8; + * if (pkt_end >= r2) goto + * + * + * Where: + * pkt_end == dst_reg, r2 == src_reg + * r2=pkt(id=n,off=8,r=0) + * r3=pkt(id=n,off=0,r=0) + * + * Find register r3 and mark its range as r3=pkt(id=n,off=0,r=8) + * so that range of bytes [r3, r3 + 8) is safe to access. */ + for (i = 0; i < MAX_BPF_REG; i++) if (regs[i].type == PTR_TO_PACKET && regs[i].id == dst_reg->id) regs[i].range = dst_reg->off; @@ -1668,8 +1689,8 @@ static void find_good_pkt_pointers(struct verifier_env *env, static int check_cond_jmp_op(struct verifier_env *env, struct bpf_insn *insn, int *insn_idx) { - struct reg_state *regs = env->cur_state.regs, *dst_reg; - struct verifier_state *other_branch; + struct verifier_state *other_branch, *this_branch = &env->cur_state; + struct reg_state *regs = this_branch->regs, *dst_reg; u8 opcode = BPF_OP(insn->code); int err; @@ -1750,13 +1771,17 @@ static int check_cond_jmp_op(struct verifier_env *env, } else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JGT && dst_reg->type == PTR_TO_PACKET && regs[insn->src_reg].type == PTR_TO_PACKET_END) { - find_good_pkt_pointers(env, dst_reg); + find_good_pkt_pointers(this_branch, dst_reg); + } else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JGE && + dst_reg->type == PTR_TO_PACKET_END && + regs[insn->src_reg].type == PTR_TO_PACKET) { + find_good_pkt_pointers(other_branch, ®s[insn->src_reg]); } else if (is_pointer_value(env, insn->dst_reg)) { verbose("R%d pointer comparison prohibited\n", insn->dst_reg); return -EACCES; } if (log_level) - print_verifier_state(&env->cur_state); + print_verifier_state(this_branch); return 0; } diff --git a/samples/bpf/test_verifier.c b/samples/bpf/test_verifier.c index 78c6f131d94f2c651e9c624ce679c369a8921e33..1f6cc9b6a23ba9a6e66f3ab83d6d651e30234952 100644 --- a/samples/bpf/test_verifier.c +++ b/samples/bpf/test_verifier.c @@ -1528,6 +1528,108 @@ static struct bpf_test tests[] = { .result = REJECT, .prog_type = BPF_PROG_TYPE_SCHED_CLS, }, + { + "direct packet access: test5 (pkt_end >= reg, good access)", + .insns = { + BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, + offsetof(struct __sk_buff, data)), + BPF_LDX_MEM(BPF_W, BPF_REG_3, BPF_REG_1, + offsetof(struct __sk_buff, data_end)), + BPF_MOV64_REG(BPF_REG_0, BPF_REG_2), + BPF_ALU64_IMM(BPF_ADD, BPF_REG_0, 8), + BPF_JMP_REG(BPF_JGE, BPF_REG_3, BPF_REG_0, 2), + BPF_MOV64_IMM(BPF_REG_0, 1), + BPF_EXIT_INSN(), + BPF_LDX_MEM(BPF_B, BPF_REG_0, BPF_REG_2, 0), + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }, + .result = ACCEPT, + .prog_type = BPF_PROG_TYPE_SCHED_CLS, + }, + { + "direct packet access: test6 (pkt_end >= reg, bad access)", + .insns = { + BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, + offsetof(struct __sk_buff, data)), + BPF_LDX_MEM(BPF_W, BPF_REG_3, BPF_REG_1, + offsetof(struct __sk_buff, data_end)), + BPF_MOV64_REG(BPF_REG_0, BPF_REG_2), + BPF_ALU64_IMM(BPF_ADD, BPF_REG_0, 8), + BPF_JMP_REG(BPF_JGE, BPF_REG_3, BPF_REG_0, 3), + BPF_LDX_MEM(BPF_B, BPF_REG_0, BPF_REG_2, 0), + BPF_MOV64_IMM(BPF_REG_0, 1), + BPF_EXIT_INSN(), + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }, + .errstr = "invalid access to packet", + .result = REJECT, + .prog_type = BPF_PROG_TYPE_SCHED_CLS, + }, + { + "direct packet access: test7 (pkt_end >= reg, both accesses)", + .insns = { + BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, + offsetof(struct __sk_buff, data)), + BPF_LDX_MEM(BPF_W, BPF_REG_3, BPF_REG_1, + offsetof(struct __sk_buff, data_end)), + BPF_MOV64_REG(BPF_REG_0, BPF_REG_2), + BPF_ALU64_IMM(BPF_ADD, BPF_REG_0, 8), + BPF_JMP_REG(BPF_JGE, BPF_REG_3, BPF_REG_0, 3), + BPF_LDX_MEM(BPF_B, BPF_REG_0, BPF_REG_2, 0), + BPF_MOV64_IMM(BPF_REG_0, 1), + BPF_EXIT_INSN(), + BPF_LDX_MEM(BPF_B, BPF_REG_0, BPF_REG_2, 0), + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }, + .errstr = "invalid access to packet", + .result = REJECT, + .prog_type = BPF_PROG_TYPE_SCHED_CLS, + }, + { + "direct packet access: test8 (double test, variant 1)", + .insns = { + BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, + offsetof(struct __sk_buff, data)), + BPF_LDX_MEM(BPF_W, BPF_REG_3, BPF_REG_1, + offsetof(struct __sk_buff, data_end)), + BPF_MOV64_REG(BPF_REG_0, BPF_REG_2), + BPF_ALU64_IMM(BPF_ADD, BPF_REG_0, 8), + BPF_JMP_REG(BPF_JGE, BPF_REG_3, BPF_REG_0, 4), + BPF_JMP_REG(BPF_JGT, BPF_REG_0, BPF_REG_3, 1), + BPF_LDX_MEM(BPF_B, BPF_REG_0, BPF_REG_2, 0), + BPF_MOV64_IMM(BPF_REG_0, 1), + BPF_EXIT_INSN(), + BPF_LDX_MEM(BPF_B, BPF_REG_0, BPF_REG_2, 0), + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }, + .result = ACCEPT, + .prog_type = BPF_PROG_TYPE_SCHED_CLS, + }, + { + "direct packet access: test9 (double test, variant 2)", + .insns = { + BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, + offsetof(struct __sk_buff, data)), + BPF_LDX_MEM(BPF_W, BPF_REG_3, BPF_REG_1, + offsetof(struct __sk_buff, data_end)), + BPF_MOV64_REG(BPF_REG_0, BPF_REG_2), + BPF_ALU64_IMM(BPF_ADD, BPF_REG_0, 8), + BPF_JMP_REG(BPF_JGE, BPF_REG_3, BPF_REG_0, 2), + BPF_MOV64_IMM(BPF_REG_0, 1), + BPF_EXIT_INSN(), + BPF_JMP_REG(BPF_JGT, BPF_REG_0, BPF_REG_3, 1), + BPF_LDX_MEM(BPF_B, BPF_REG_0, BPF_REG_2, 0), + BPF_LDX_MEM(BPF_B, BPF_REG_0, BPF_REG_2, 0), + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }, + .result = ACCEPT, + .prog_type = BPF_PROG_TYPE_SCHED_CLS, + }, { "helper access to packet: test1, valid packet_ptr range", .insns = {