diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 9f81818f2941..b6a1f7c14a67 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -153,22 +153,19 @@ struct reg_state { enum bpf_stack_slot_type { STACK_INVALID, /* nothing was stored in this stack slot */ - STACK_SPILL, /* 1st byte of register spilled into stack */ - STACK_SPILL_PART, /* other 7 bytes of register spill */ + STACK_SPILL, /* register spilled into stack */ STACK_MISC /* BPF program wrote some data into this slot */ }; -struct bpf_stack_slot { - enum bpf_stack_slot_type stype; - struct reg_state reg_st; -}; +#define BPF_REG_SIZE 8 /* size of eBPF register in bytes */ /* state of the program: * type of all registers and stack info */ struct verifier_state { struct reg_state regs[MAX_BPF_REG]; - struct bpf_stack_slot stack[MAX_BPF_STACK]; + u8 stack_slot_type[MAX_BPF_STACK]; + struct reg_state spilled_regs[MAX_BPF_STACK / BPF_REG_SIZE]; }; /* linked list of verifier states used to prune search */ @@ -259,10 +256,10 @@ static void print_verifier_state(struct verifier_env *env) env->cur_state.regs[i].map_ptr->key_size, env->cur_state.regs[i].map_ptr->value_size); } - for (i = 0; i < MAX_BPF_STACK; i++) { - if (env->cur_state.stack[i].stype == STACK_SPILL) + for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) { + if (env->cur_state.stack_slot_type[i] == STACK_SPILL) verbose(" fp%d=%s", -MAX_BPF_STACK + i, - reg_type_str[env->cur_state.stack[i].reg_st.type]); + reg_type_str[env->cur_state.spilled_regs[i / BPF_REG_SIZE].type]); } verbose("\n"); } @@ -539,8 +536,10 @@ static int bpf_size_to_bytes(int bpf_size) static int check_stack_write(struct verifier_state *state, int off, int size, int value_regno) { - struct bpf_stack_slot *slot; int i; + /* caller checked that off % size == 0 and -MAX_BPF_STACK <= off < 0, + * so it's aligned access and [off, off + size) are within stack limits + */ if (value_regno >= 0 && (state->regs[value_regno].type == PTR_TO_MAP_VALUE || @@ -548,30 +547,24 @@ static int check_stack_write(struct verifier_state *state, int off, int size, state->regs[value_regno].type == PTR_TO_CTX)) { /* register containing pointer is being spilled into stack */ - if (size != 8) { + if (size != BPF_REG_SIZE) { verbose("invalid size of register spill\n"); return -EACCES; } - slot = &state->stack[MAX_BPF_STACK + off]; - slot->stype = STACK_SPILL; /* save register state */ - slot->reg_st = state->regs[value_regno]; - for (i = 1; i < 8; i++) { - slot = &state->stack[MAX_BPF_STACK + off + i]; - slot->stype = STACK_SPILL_PART; - slot->reg_st.type = UNKNOWN_VALUE; - slot->reg_st.map_ptr = NULL; - } - } else { + state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] = + state->regs[value_regno]; + for (i = 0; i < BPF_REG_SIZE; i++) + state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_SPILL; + } else { /* regular write of data into stack */ - for (i = 0; i < size; i++) { - slot = &state->stack[MAX_BPF_STACK + off + i]; - slot->stype = STACK_MISC; - slot->reg_st.type = UNKNOWN_VALUE; - slot->reg_st.map_ptr = NULL; - } + state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] = + (struct reg_state) {}; + + for (i = 0; i < size; i++) + state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_MISC; } return 0; } @@ -579,19 +572,18 @@ static int check_stack_write(struct verifier_state *state, int off, int size, static int check_stack_read(struct verifier_state *state, int off, int size, int value_regno) { + u8 *slot_type; int i; - struct bpf_stack_slot *slot; - slot = &state->stack[MAX_BPF_STACK + off]; + slot_type = &state->stack_slot_type[MAX_BPF_STACK + off]; - if (slot->stype == STACK_SPILL) { - if (size != 8) { + if (slot_type[0] == STACK_SPILL) { + if (size != BPF_REG_SIZE) { verbose("invalid size of register spill\n"); return -EACCES; } - for (i = 1; i < 8; i++) { - if (state->stack[MAX_BPF_STACK + off + i].stype != - STACK_SPILL_PART) { + for (i = 1; i < BPF_REG_SIZE; i++) { + if (slot_type[i] != STACK_SPILL) { verbose("corrupted spill memory\n"); return -EACCES; } @@ -599,12 +591,12 @@ static int check_stack_read(struct verifier_state *state, int off, int size, if (value_regno >= 0) /* restore register state from stack */ - state->regs[value_regno] = slot->reg_st; + state->regs[value_regno] = + state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE]; return 0; } else { for (i = 0; i < size; i++) { - if (state->stack[MAX_BPF_STACK + off + i].stype != - STACK_MISC) { + if (slot_type[i] != STACK_MISC) { verbose("invalid read from stack off %d+%d size %d\n", off, i, size); return -EACCES; @@ -747,7 +739,7 @@ static int check_stack_boundary(struct verifier_env *env, } for (i = 0; i < access_size; i++) { - if (state->stack[MAX_BPF_STACK + off + i].stype != STACK_MISC) { + if (state->stack_slot_type[MAX_BPF_STACK + off + i] != STACK_MISC) { verbose("invalid indirect read from stack off %d+%d size %d\n", off, i, access_size); return -EACCES; @@ -1417,12 +1409,33 @@ static bool states_equal(struct verifier_state *old, struct verifier_state *cur) } for (i = 0; i < MAX_BPF_STACK; i++) { - if (memcmp(&old->stack[i], &cur->stack[i], - sizeof(old->stack[0])) != 0) { - if (old->stack[i].stype == STACK_INVALID) - continue; + if (old->stack_slot_type[i] == STACK_INVALID) + continue; + if (old->stack_slot_type[i] != cur->stack_slot_type[i]) + /* Ex: old explored (safe) state has STACK_SPILL in + * this stack slot, but current has has STACK_MISC -> + * this verifier states are not equivalent, + * return false to continue verification of this path + */ return false; - } + if (i % BPF_REG_SIZE) + continue; + if (memcmp(&old->spilled_regs[i / BPF_REG_SIZE], + &cur->spilled_regs[i / BPF_REG_SIZE], + sizeof(old->spilled_regs[0]))) + /* when explored and current stack slot types are + * the same, check that stored pointers types + * are the same as well. + * Ex: explored safe path could have stored + * (struct reg_state) {.type = PTR_TO_STACK, .imm = -8} + * but current path has stored: + * (struct reg_state) {.type = PTR_TO_STACK, .imm = -16} + * such verifier states are not equivalent. + * return false to continue verification of this path + */ + return false; + else + continue; } return true; }