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Merge branch 'bpf-verifier-misc-improvements'
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Alexei Starovoitov says:

====================
Small set of verifier improvements and cleanups which is
necessary for bigger patch set of bpf-to-bpf calls coming later.
See individual patches for details.
Tested on x86 and arm64 hw.
====================

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
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Daniel Borkmann committed Dec 1, 2017
2 parents 51de082 + 6a28b44 commit 554b36b
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Showing 2 changed files with 120 additions and 98 deletions.
62 changes: 42 additions & 20 deletions kernel/bpf/verifier.c
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Original file line number Diff line number Diff line change
Expand Up @@ -216,6 +216,17 @@ static const char * const reg_type_str[] = {
[PTR_TO_PACKET_END] = "pkt_end",
};

static void print_liveness(struct bpf_verifier_env *env,
enum bpf_reg_liveness live)
{
if (live & (REG_LIVE_READ | REG_LIVE_WRITTEN))
verbose(env, "_");
if (live & REG_LIVE_READ)
verbose(env, "r");
if (live & REG_LIVE_WRITTEN)
verbose(env, "w");
}

static void print_verifier_state(struct bpf_verifier_env *env,
struct bpf_verifier_state *state)
{
Expand All @@ -228,7 +239,9 @@ static void print_verifier_state(struct bpf_verifier_env *env,
t = reg->type;
if (t == NOT_INIT)
continue;
verbose(env, " R%d=%s", i, reg_type_str[t]);
verbose(env, " R%d", i);
print_liveness(env, reg->live);
verbose(env, "=%s", reg_type_str[t]);
if ((t == SCALAR_VALUE || t == PTR_TO_STACK) &&
tnum_is_const(reg->var_off)) {
/* reg->off should be 0 for SCALAR_VALUE */
Expand Down Expand Up @@ -277,10 +290,13 @@ static void print_verifier_state(struct bpf_verifier_env *env,
}
}
for (i = 0; i < state->allocated_stack / BPF_REG_SIZE; i++) {
if (state->stack[i].slot_type[0] == STACK_SPILL)
verbose(env, " fp%d=%s",
-MAX_BPF_STACK + i * BPF_REG_SIZE,
if (state->stack[i].slot_type[0] == STACK_SPILL) {
verbose(env, " fp%d",
(-i - 1) * BPF_REG_SIZE);
print_liveness(env, state->stack[i].spilled_ptr.live);
verbose(env, "=%s",
reg_type_str[state->stack[i].spilled_ptr.type]);
}
}
verbose(env, "\n");
}
Expand Down Expand Up @@ -568,8 +584,8 @@ static void mark_reg_unknown(struct bpf_verifier_env *env,
{
if (WARN_ON(regno >= MAX_BPF_REG)) {
verbose(env, "mark_reg_unknown(regs, %u)\n", regno);
/* Something bad happened, let's kill all regs */
for (regno = 0; regno < MAX_BPF_REG; regno++)
/* Something bad happened, let's kill all regs except FP */
for (regno = 0; regno < BPF_REG_FP; regno++)
__mark_reg_not_init(regs + regno);
return;
}
Expand All @@ -587,8 +603,8 @@ static void mark_reg_not_init(struct bpf_verifier_env *env,
{
if (WARN_ON(regno >= MAX_BPF_REG)) {
verbose(env, "mark_reg_not_init(regs, %u)\n", regno);
/* Something bad happened, let's kill all regs */
for (regno = 0; regno < MAX_BPF_REG; regno++)
/* Something bad happened, let's kill all regs except FP */
for (regno = 0; regno < BPF_REG_FP; regno++)
__mark_reg_not_init(regs + regno);
return;
}
Expand Down Expand Up @@ -779,6 +795,11 @@ static int check_stack_read(struct bpf_verifier_env *env,
if (value_regno >= 0) {
/* restore register state from stack */
state->regs[value_regno] = state->stack[spi].spilled_ptr;
/* mark reg as written since spilled pointer state likely
* has its liveness marks cleared by is_state_visited()
* which resets stack/reg liveness for state transitions
*/
state->regs[value_regno].live |= REG_LIVE_WRITTEN;
mark_stack_slot_read(state, spi);
}
return 0;
Expand Down Expand Up @@ -1244,9 +1265,9 @@ static int check_xadd(struct bpf_verifier_env *env, int insn_idx, struct bpf_ins
}

/* Does this register contain a constant zero? */
static bool register_is_null(struct bpf_reg_state reg)
static bool register_is_null(struct bpf_reg_state *reg)
{
return reg.type == SCALAR_VALUE && tnum_equals_const(reg.var_off, 0);
return reg->type == SCALAR_VALUE && tnum_equals_const(reg->var_off, 0);
}

/* when register 'regno' is passed into function that will read 'access_size'
Expand All @@ -1259,31 +1280,31 @@ static int check_stack_boundary(struct bpf_verifier_env *env, int regno,
int access_size, bool zero_size_allowed,
struct bpf_call_arg_meta *meta)
{
struct bpf_reg_state *reg = cur_regs(env) + regno;
struct bpf_verifier_state *state = env->cur_state;
struct bpf_reg_state *regs = state->regs;
int off, i, slot, spi;

if (regs[regno].type != PTR_TO_STACK) {
if (reg->type != PTR_TO_STACK) {
/* Allow zero-byte read from NULL, regardless of pointer type */
if (zero_size_allowed && access_size == 0 &&
register_is_null(regs[regno]))
register_is_null(reg))
return 0;

verbose(env, "R%d type=%s expected=%s\n", regno,
reg_type_str[regs[regno].type],
reg_type_str[reg->type],
reg_type_str[PTR_TO_STACK]);
return -EACCES;
}

/* Only allow fixed-offset stack reads */
if (!tnum_is_const(regs[regno].var_off)) {
if (!tnum_is_const(reg->var_off)) {
char tn_buf[48];

tnum_strn(tn_buf, sizeof(tn_buf), regs[regno].var_off);
tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
verbose(env, "invalid variable stack read R%d var_off=%s\n",
regno, tn_buf);
}
off = regs[regno].off + regs[regno].var_off.value;
off = reg->off + reg->var_off.value;
if (off >= 0 || off < -MAX_BPF_STACK || off + access_size > 0 ||
access_size < 0 || (access_size == 0 && !zero_size_allowed)) {
verbose(env, "invalid stack type R%d off=%d access_size=%d\n",
Expand Down Expand Up @@ -1391,7 +1412,7 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 regno,
* passed in as argument, it's a SCALAR_VALUE type. Final test
* happens during stack boundary checking.
*/
if (register_is_null(*reg) &&
if (register_is_null(reg) &&
arg_type == ARG_PTR_TO_MEM_OR_NULL)
/* final test in check_stack_boundary() */;
else if (!type_is_pkt_pointer(type) &&
Expand Down Expand Up @@ -2934,8 +2955,9 @@ static int check_cond_jmp_op(struct bpf_verifier_env *env,
if (BPF_SRC(insn->code) == BPF_K &&
(opcode == BPF_JEQ || opcode == BPF_JNE) &&
dst_reg->type == SCALAR_VALUE &&
tnum_equals_const(dst_reg->var_off, insn->imm)) {
if (opcode == BPF_JEQ) {
tnum_is_const(dst_reg->var_off)) {
if ((opcode == BPF_JEQ && dst_reg->var_off.value == insn->imm) ||
(opcode == BPF_JNE && dst_reg->var_off.value != insn->imm)) {
/* if (imm == imm) goto pc+off;
* only follow the goto, ignore fall-through
*/
Expand Down
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