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bpf: Improve verifier error messages for users

Consolidate all error handling and provide more user-friendly error messages from sanitize_ptr_alu() and sanitize_val_alu().

Daniel Borkmann committed 5 years ago

Commit a6aaece1 parent b658bbb1 file · +63 −23Browse files

Showing the changes to kernel (1 of 1 file). Show all

Unified · Split

kernel/bpf/verifier.c+63−23
@@ -5856,6 +5856,14 @@ static struct bpf_insn_aux_data *cur_aux(struct bpf_verifier_env *env) · 5855 unmodified lines
5856 return &env->insn_aux_data[env->insn_idx];5856 return &env->insn_aux_data[env->insn_idx];
5857}5857}
5858 5858
5859enum {
5860 REASON_BOUNDS = -1,
5861 REASON_TYPE = -2,
5862 REASON_PATHS = -3,
5863 REASON_LIMIT = -4,
5864 REASON_STACK = -5,
5865};
5866
5859static int retrieve_ptr_limit(const struct bpf_reg_state *ptr_reg,5867static int retrieve_ptr_limit(const struct bpf_reg_state *ptr_reg,
5860 const struct bpf_reg_state *off_reg,5868 const struct bpf_reg_state *off_reg,
5861 u32 *alu_limit, u8 opcode)5869 u32 *alu_limit, u8 opcode)
@@ -5867,7 +5875,7 @@ static int retrieve_ptr_limit(const struct bpf_reg_state *ptr_reg, · 5 unmodified lines
5867 5875
5868 if (!tnum_is_const(off_reg->var_off) &&5876 if (!tnum_is_const(off_reg->var_off) &&
5869 (off_reg->smin_value < 0) != (off_reg->smax_value < 0))5877 (off_reg->smin_value < 0) != (off_reg->smax_value < 0))
5870 return -EACCES;5878 return REASON_BOUNDS;
5871 5879
5872 switch (ptr_reg->type) {5880 switch (ptr_reg->type) {
5873 case PTR_TO_STACK:5881 case PTR_TO_STACK:
@@ -5894,11 +5902,11 @@ static int retrieve_ptr_limit(const struct bpf_reg_state *ptr_reg, · 20 unmodified lines
5894 }5902 }
5895 break;5903 break;
5896 default:5904 default:
5897 return -EINVAL;5905 return REASON_TYPE;
5898 }5906 }
5899 5907
5900 if (ptr_limit >= max)5908 if (ptr_limit >= max)
5901 return -ERANGE;5909 return REASON_LIMIT;
5902 *alu_limit = ptr_limit;5910 *alu_limit = ptr_limit;
5903 return 0;5911 return 0;
5904}5912}
@@ -5918,7 +5926,7 @@ static int update_alu_sanitation_state(struct bpf_insn_aux_data *aux, · 13 unmodified lines
5918 if (aux->alu_state &&5926 if (aux->alu_state &&
5919 (aux->alu_state != alu_state ||5927 (aux->alu_state != alu_state ||
5920 aux->alu_limit != alu_limit))5928 aux->alu_limit != alu_limit))
5921 return -EACCES;5929 return REASON_PATHS;
5922 5930
5923 /* Corresponding fixup done in fixup_bpf_calls(). */5931 /* Corresponding fixup done in fixup_bpf_calls(). */
5924 aux->alu_state = alu_state;5932 aux->alu_state = alu_state;
@@ -5991,7 +5999,46 @@ do_sim: · 66 unmodified lines
5991 ret = push_stack(env, env->insn_idx + 1, env->insn_idx, true);5999 ret = push_stack(env, env->insn_idx + 1, env->insn_idx, true);
5992 if (!ptr_is_dst_reg && ret)6000 if (!ptr_is_dst_reg && ret)
5993 *dst_reg = tmp;6001 *dst_reg = tmp;
5994 return !ret ? -EFAULT : 0;6002 return !ret ? REASON_STACK : 0;
6003}
6004
6005static int sanitize_err(struct bpf_verifier_env *env,
6006 const struct bpf_insn *insn, int reason,
6007 const struct bpf_reg_state *off_reg,
6008 const struct bpf_reg_state *dst_reg)
6009{
6010 static const char *err = "pointer arithmetic with it prohibited for !root";
6011 const char *op = BPF_OP(insn->code) == BPF_ADD ? "add" : "sub";
6012 u32 dst = insn->dst_reg, src = insn->src_reg;
6013
6014 switch (reason) {
6015 case REASON_BOUNDS:
6016 verbose(env, "R%d has unknown scalar with mixed signed bounds, %s\n",
6017 off_reg == dst_reg ? dst : src, err);
6018 break;
6019 case REASON_TYPE:
6020 verbose(env, "R%d has pointer with unsupported alu operation, %s\n",
6021 off_reg == dst_reg ? src : dst, err);
6022 break;
6023 case REASON_PATHS:
6024 verbose(env, "R%d tried to %s from different maps, paths or scalars, %s\n",
6025 dst, op, err);
6026 break;
6027 case REASON_LIMIT:
6028 verbose(env, "R%d tried to %s beyond pointer bounds, %s\n",
6029 dst, op, err);
6030 break;
6031 case REASON_STACK:
6032 verbose(env, "R%d could not be pushed for speculative verification, %s\n",
6033 dst, err);
6034 break;
6035 default:
6036 verbose(env, "verifier internal error: unknown reason (%d)\n",
6037 reason);
6038 break;
6039 }
6040
6041 return -EACCES;
5995}6042}
5996 6043
5997/* check that stack access falls within stack limits and that 'reg' doesn't6044/* check that stack access falls within stack limits and that 'reg' doesn't
@@ -6116,10 +6163,9 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env, · 118 unmodified lines
6116 switch (opcode) {6163 switch (opcode) {
6117 case BPF_ADD:6164 case BPF_ADD:
6118 ret = sanitize_ptr_alu(env, insn, ptr_reg, off_reg, dst_reg);6165 ret = sanitize_ptr_alu(env, insn, ptr_reg, off_reg, dst_reg);
6119 if (ret < 0) {6166 if (ret < 0)
6120 verbose(env, "R%d tried to add from different maps, paths, or prohibited types\n", dst);6167 return sanitize_err(env, insn, ret, off_reg, dst_reg);
6121 return ret;6168
6122 }
6123 /* We can take a fixed offset as long as it doesn't overflow6169 /* We can take a fixed offset as long as it doesn't overflow
6124 * the s32 'off' field6170 * the s32 'off' field
6125 */6171 */
@@ -6171,10 +6217,9 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env, · 45 unmodified lines
6171 break;6217 break;
6172 case BPF_SUB:6218 case BPF_SUB:
6173 ret = sanitize_ptr_alu(env, insn, ptr_reg, off_reg, dst_reg);6219 ret = sanitize_ptr_alu(env, insn, ptr_reg, off_reg, dst_reg);
6174 if (ret < 0) {6220 if (ret < 0)
6175 verbose(env, "R%d tried to sub from different maps, paths, or prohibited types\n", dst);6221 return sanitize_err(env, insn, ret, off_reg, dst_reg);
6176 return ret;6222
6177 }
6178 if (dst_reg == off_reg) {6223 if (dst_reg == off_reg) {
6179 /* scalar -= pointer. Creates an unknown scalar */6224 /* scalar -= pointer. Creates an unknown scalar */
6180 verbose(env, "R%d tried to subtract pointer from scalar\n",6225 verbose(env, "R%d tried to subtract pointer from scalar\n",
@@ -6863,9 +6908,8 @@ static int adjust_scalar_min_max_vals(struct bpf_verifier_env *env, · 682 unmodified lines
6863 s32 s32_min_val, s32_max_val;6908 s32 s32_min_val, s32_max_val;
6864 u32 u32_min_val, u32_max_val;6909 u32 u32_min_val, u32_max_val;
6865 u64 insn_bitness = (BPF_CLASS(insn->code) == BPF_ALU64) ? 64 : 32;6910 u64 insn_bitness = (BPF_CLASS(insn->code) == BPF_ALU64) ? 64 : 32;
6866 u32 dst = insn->dst_reg;
6867 int ret;
6868 bool alu32 = (BPF_CLASS(insn->code) != BPF_ALU64);6911 bool alu32 = (BPF_CLASS(insn->code) != BPF_ALU64);
6912 int ret;
6869 6913
6870 smin_val = src_reg.smin_value;6914 smin_val = src_reg.smin_value;
6871 smax_val = src_reg.smax_value;6915 smax_val = src_reg.smax_value;
@@ -6924,20 +6968,16 @@ static int adjust_scalar_min_max_vals(struct bpf_verifier_env *env, · 52 unmodified lines
6924 switch (opcode) {6968 switch (opcode) {
6925 case BPF_ADD:6969 case BPF_ADD:
6926 ret = sanitize_val_alu(env, insn);6970 ret = sanitize_val_alu(env, insn);
6927 if (ret < 0) {6971 if (ret < 0)
6928 verbose(env, "R%d tried to add from different pointers or scalars\n", dst);6972 return sanitize_err(env, insn, ret, NULL, NULL);
6929 return ret;
6930 }
6931 scalar32_min_max_add(dst_reg, &src_reg);6973 scalar32_min_max_add(dst_reg, &src_reg);
6932 scalar_min_max_add(dst_reg, &src_reg);6974 scalar_min_max_add(dst_reg, &src_reg);
6933 dst_reg->var_off = tnum_add(dst_reg->var_off, src_reg.var_off);6975 dst_reg->var_off = tnum_add(dst_reg->var_off, src_reg.var_off);
6934 break;6976 break;
6935 case BPF_SUB:6977 case BPF_SUB:
6936 ret = sanitize_val_alu(env, insn);6978 ret = sanitize_val_alu(env, insn);
6937 if (ret < 0) {6979 if (ret < 0)
6938 verbose(env, "R%d tried to sub from different pointers or scalars\n", dst);6980 return sanitize_err(env, insn, ret, NULL, NULL);
6939 return ret;
6940 }
6941 scalar32_min_max_sub(dst_reg, &src_reg);6981 scalar32_min_max_sub(dst_reg, &src_reg);
6942 scalar_min_max_sub(dst_reg, &src_reg);6982 scalar_min_max_sub(dst_reg, &src_reg);
6943 dst_reg->var_off = tnum_sub(dst_reg->var_off, src_reg.var_off);6983 dst_reg->var_off = tnum_sub(dst_reg->var_off, src_reg.var_off);