diff options
Diffstat (limited to 'kernel/bpf/verifier.c')
-rw-r--r-- | kernel/bpf/verifier.c | 98 |
1 files changed, 77 insertions, 21 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 35dfa9e9d69e..c43ca9857479 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -191,6 +191,7 @@ struct bpf_insn_aux_data { enum bpf_reg_type ptr_type; /* pointer type for load/store insns */ struct bpf_map *map_ptr; /* pointer for call insn into lookup_elem */ }; + int sanitize_stack_off; /* stack slot to be cleared */ bool seen; /* this insn was processed by the verifier */ }; @@ -569,10 +570,11 @@ static bool is_spillable_regtype(enum bpf_reg_type type) /* check_stack_read/write functions track spill/fill of registers, * stack boundary and alignment are checked in check_mem_access() */ -static int check_stack_write(struct verifier_state *state, int off, int size, - int value_regno) +static int check_stack_write(struct verifier_env *env, + struct verifier_state *state, int off, + int size, int value_regno, int insn_idx) { - int i; + int i, spi = (MAX_BPF_STACK + off) / BPF_REG_SIZE; /* 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 */ @@ -587,15 +589,37 @@ static int check_stack_write(struct verifier_state *state, int off, int size, } /* save register state */ - state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] = - state->regs[value_regno]; - - for (i = 0; i < BPF_REG_SIZE; i++) + state->spilled_regs[spi] = state->regs[value_regno]; + + for (i = 0; i < BPF_REG_SIZE; i++) { + if (state->stack_slot_type[MAX_BPF_STACK + off + i] == STACK_MISC && + !env->allow_ptr_leaks) { + int *poff = &env->insn_aux_data[insn_idx].sanitize_stack_off; + int soff = (-spi - 1) * BPF_REG_SIZE; + + /* detected reuse of integer stack slot with a pointer + * which means either llvm is reusing stack slot or + * an attacker is trying to exploit CVE-2018-3639 + * (speculative store bypass) + * Have to sanitize that slot with preemptive + * store of zero. + */ + if (*poff && *poff != soff) { + /* disallow programs where single insn stores + * into two different stack slots, since verifier + * cannot sanitize them + */ + verbose("insn %d cannot access two stack slots fp%d and fp%d", + insn_idx, *poff, soff); + return -EINVAL; + } + *poff = soff; + } state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_SPILL; + } } else { /* regular write of data into stack */ - state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] = - (struct reg_state) {}; + state->spilled_regs[spi] = (struct reg_state) {}; for (i = 0; i < size; i++) state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_MISC; @@ -696,7 +720,7 @@ static bool is_ctx_reg(struct verifier_env *env, int regno) * if t==write && value_regno==-1, some unknown value is stored into memory * if t==read && value_regno==-1, don't care what we read from memory */ -static int check_mem_access(struct verifier_env *env, u32 regno, int off, +static int check_mem_access(struct verifier_env *env, int insn_idx, u32 regno, int off, int bpf_size, enum bpf_access_type t, int value_regno) { @@ -748,7 +772,8 @@ static int check_mem_access(struct verifier_env *env, u32 regno, int off, verbose("attempt to corrupt spilled pointer on stack\n"); return -EACCES; } - err = check_stack_write(state, off, size, value_regno); + err = check_stack_write(env, state, off, size, + value_regno, insn_idx); } else { err = check_stack_read(state, off, size, value_regno); } @@ -760,7 +785,7 @@ static int check_mem_access(struct verifier_env *env, u32 regno, int off, return err; } -static int check_xadd(struct verifier_env *env, struct bpf_insn *insn) +static int check_xadd(struct verifier_env *env, int insn_idx, struct bpf_insn *insn) { struct reg_state *regs = env->cur_state.regs; int err; @@ -793,13 +818,13 @@ static int check_xadd(struct verifier_env *env, struct bpf_insn *insn) } /* check whether atomic_add can read the memory */ - err = check_mem_access(env, insn->dst_reg, insn->off, + err = check_mem_access(env, insn_idx, insn->dst_reg, insn->off, BPF_SIZE(insn->code), BPF_READ, -1); if (err) return err; /* check whether atomic_add can write into the same memory */ - return check_mem_access(env, insn->dst_reg, insn->off, + return check_mem_access(env, insn_idx, insn->dst_reg, insn->off, BPF_SIZE(insn->code), BPF_WRITE, -1); } @@ -1838,13 +1863,14 @@ static int do_check(struct verifier_env *env) /* check that memory (src_reg + off) is readable, * the state of dst_reg will be updated by this func */ - err = check_mem_access(env, insn->src_reg, insn->off, + err = check_mem_access(env, insn_idx, insn->src_reg, insn->off, BPF_SIZE(insn->code), BPF_READ, insn->dst_reg); if (err) return err; - if (BPF_SIZE(insn->code) != BPF_W) { + if (BPF_SIZE(insn->code) != BPF_W && + BPF_SIZE(insn->code) != BPF_DW) { insn_idx++; continue; } @@ -1876,7 +1902,7 @@ static int do_check(struct verifier_env *env) enum bpf_reg_type *prev_dst_type, dst_reg_type; if (BPF_MODE(insn->code) == BPF_XADD) { - err = check_xadd(env, insn); + err = check_xadd(env, insn_idx, insn); if (err) return err; insn_idx++; @@ -1895,7 +1921,7 @@ static int do_check(struct verifier_env *env) dst_reg_type = regs[insn->dst_reg].type; /* check that memory (dst_reg + off) is writeable */ - err = check_mem_access(env, insn->dst_reg, insn->off, + err = check_mem_access(env, insn_idx, insn->dst_reg, insn->off, BPF_SIZE(insn->code), BPF_WRITE, insn->src_reg); if (err) @@ -1930,7 +1956,7 @@ static int do_check(struct verifier_env *env) } /* check that memory (dst_reg + off) is writeable */ - err = check_mem_access(env, insn->dst_reg, insn->off, + err = check_mem_access(env, insn_idx, insn->dst_reg, insn->off, BPF_SIZE(insn->code), BPF_WRITE, -1); if (err) @@ -2220,13 +2246,43 @@ static int convert_ctx_accesses(struct verifier_env *env) for (i = 0; i < insn_cnt; i++, insn++) { u32 cnt; - if (insn->code == (BPF_LDX | BPF_MEM | BPF_W)) + if (insn->code == (BPF_LDX | BPF_MEM | BPF_W) || + insn->code == (BPF_LDX | BPF_MEM | BPF_DW)) type = BPF_READ; - else if (insn->code == (BPF_STX | BPF_MEM | BPF_W)) + else if (insn->code == (BPF_STX | BPF_MEM | BPF_W) || + insn->code == (BPF_STX | BPF_MEM | BPF_DW)) type = BPF_WRITE; else continue; + if (type == BPF_WRITE && + env->insn_aux_data[i + delta].sanitize_stack_off) { + struct bpf_insn patch[] = { + /* Sanitize suspicious stack slot with zero. + * There are no memory dependencies for this store, + * since it's only using frame pointer and immediate + * constant of zero + */ + BPF_ST_MEM(BPF_DW, BPF_REG_FP, + env->insn_aux_data[i + delta].sanitize_stack_off, + 0), + /* the original STX instruction will immediately + * overwrite the same stack slot with appropriate value + */ + *insn, + }; + + cnt = ARRAY_SIZE(patch); + new_prog = bpf_patch_insn_data(env, i + delta, patch, cnt); + if (!new_prog) + return -ENOMEM; + + delta += cnt - 1; + env->prog = new_prog; + insn = new_prog->insnsi + i + delta; + continue; + } + if (env->insn_aux_data[i + delta].ptr_type != PTR_TO_CTX) continue; |