aboutsummaryrefslogtreecommitdiff
path: root/kernel/bpf/verifier.c
diff options
context:
space:
mode:
Diffstat (limited to 'kernel/bpf/verifier.c')
-rw-r--r--kernel/bpf/verifier.c111
1 files changed, 99 insertions, 12 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 372454aa7f37..d7eeebfafe8d 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1790,10 +1790,17 @@ static int check_alu_op(struct bpf_verifier_env *env, struct bpf_insn *insn)
/* case: R = imm
* remember the value we stored into this reg
*/
+ u64 imm;
+
+ if (BPF_CLASS(insn->code) == BPF_ALU64)
+ imm = insn->imm;
+ else
+ imm = (u32)insn->imm;
+
regs[insn->dst_reg].type = CONST_IMM;
- regs[insn->dst_reg].imm = insn->imm;
- regs[insn->dst_reg].max_value = insn->imm;
- regs[insn->dst_reg].min_value = insn->imm;
+ regs[insn->dst_reg].imm = imm;
+ regs[insn->dst_reg].max_value = imm;
+ regs[insn->dst_reg].min_value = imm;
}
} else if (opcode > BPF_END) {
@@ -1861,10 +1868,28 @@ static int check_alu_op(struct bpf_verifier_env *env, struct bpf_insn *insn)
((BPF_SRC(insn->code) == BPF_X &&
regs[insn->src_reg].type == CONST_IMM) ||
BPF_SRC(insn->code) == BPF_K)) {
- if (BPF_SRC(insn->code) == BPF_X)
+ if (BPF_SRC(insn->code) == BPF_X) {
+ /* check in case the register contains a big
+ * 64-bit value
+ */
+ if (regs[insn->src_reg].imm < -MAX_BPF_STACK ||
+ regs[insn->src_reg].imm > MAX_BPF_STACK) {
+ verbose("R%d value too big in R%d pointer arithmetic\n",
+ insn->src_reg, insn->dst_reg);
+ return -EACCES;
+ }
dst_reg->imm += regs[insn->src_reg].imm;
- else
+ } else {
+ /* safe against overflow: addition of 32-bit
+ * numbers in 64-bit representation
+ */
dst_reg->imm += insn->imm;
+ }
+ if (dst_reg->imm > 0 || dst_reg->imm < -MAX_BPF_STACK) {
+ verbose("R%d out-of-bounds pointer arithmetic\n",
+ insn->dst_reg);
+ return -EACCES;
+ }
return 0;
} else if (opcode == BPF_ADD &&
BPF_CLASS(insn->code) == BPF_ALU64 &&
@@ -2697,11 +2722,12 @@ static bool states_equal(struct bpf_verifier_env *env,
/* If we didn't map access then again we don't care about the
* mismatched range values and it's ok if our old type was
- * UNKNOWN and we didn't go to a NOT_INIT'ed reg.
+ * UNKNOWN and we didn't go to a NOT_INIT'ed or pointer reg.
*/
if (rold->type == NOT_INIT ||
(!varlen_map_access && rold->type == UNKNOWN_VALUE &&
- rcur->type != NOT_INIT))
+ rcur->type != NOT_INIT &&
+ !__is_pointer_value(env->allow_ptr_leaks, rcur)))
continue;
/* Don't care about the reg->id in this case. */
@@ -2862,6 +2888,7 @@ static int do_check(struct bpf_verifier_env *env)
if (err)
return err;
+ env->insn_aux_data[insn_idx].seen = true;
if (class == BPF_ALU || class == BPF_ALU64) {
err = check_alu_op(env, insn);
if (err)
@@ -3059,6 +3086,7 @@ process_bpf_exit:
return err;
insn_idx++;
+ env->insn_aux_data[insn_idx].seen = true;
} else {
verbose("invalid BPF_LD mode\n");
return -EINVAL;
@@ -3210,6 +3238,63 @@ static void convert_pseudo_ld_imm64(struct bpf_verifier_env *env)
insn->src_reg = 0;
}
+/* single env->prog->insni[off] instruction was replaced with the range
+ * insni[off, off + cnt). Adjust corresponding insn_aux_data by copying
+ * [0, off) and [off, end) to new locations, so the patched range stays zero
+ */
+static int adjust_insn_aux_data(struct bpf_verifier_env *env, u32 prog_len,
+ u32 off, u32 cnt)
+{
+ struct bpf_insn_aux_data *new_data, *old_data = env->insn_aux_data;
+ int i;
+
+ if (cnt == 1)
+ return 0;
+ new_data = vzalloc(sizeof(struct bpf_insn_aux_data) * prog_len);
+ if (!new_data)
+ return -ENOMEM;
+ memcpy(new_data, old_data, sizeof(struct bpf_insn_aux_data) * off);
+ memcpy(new_data + off + cnt - 1, old_data + off,
+ sizeof(struct bpf_insn_aux_data) * (prog_len - off - cnt + 1));
+ for (i = off; i < off + cnt - 1; i++)
+ new_data[i].seen = true;
+ env->insn_aux_data = new_data;
+ vfree(old_data);
+ return 0;
+}
+
+static struct bpf_prog *bpf_patch_insn_data(struct bpf_verifier_env *env, u32 off,
+ const struct bpf_insn *patch, u32 len)
+{
+ struct bpf_prog *new_prog;
+
+ new_prog = bpf_patch_insn_single(env->prog, off, patch, len);
+ if (!new_prog)
+ return NULL;
+ if (adjust_insn_aux_data(env, new_prog->len, off, len))
+ return NULL;
+ return new_prog;
+}
+
+/* The verifier does more data flow analysis than llvm and will not explore
+ * branches that are dead at run time. Malicious programs can have dead code
+ * too. Therefore replace all dead at-run-time code with nops.
+ */
+static void sanitize_dead_code(struct bpf_verifier_env *env)
+{
+ struct bpf_insn_aux_data *aux_data = env->insn_aux_data;
+ struct bpf_insn nop = BPF_MOV64_REG(BPF_REG_0, BPF_REG_0);
+ struct bpf_insn *insn = env->prog->insnsi;
+ const int insn_cnt = env->prog->len;
+ int i;
+
+ for (i = 0; i < insn_cnt; i++) {
+ if (aux_data[i].seen)
+ continue;
+ memcpy(insn + i, &nop, sizeof(nop));
+ }
+}
+
/* convert load instructions that access fields of 'struct __sk_buff'
* into sequence of instructions that access fields of 'struct sk_buff'
*/
@@ -3229,10 +3314,10 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env)
verbose("bpf verifier is misconfigured\n");
return -EINVAL;
} else if (cnt) {
- new_prog = bpf_patch_insn_single(env->prog, 0,
- insn_buf, cnt);
+ new_prog = bpf_patch_insn_data(env, 0, insn_buf, cnt);
if (!new_prog)
return -ENOMEM;
+
env->prog = new_prog;
delta += cnt - 1;
}
@@ -3253,7 +3338,7 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env)
else
continue;
- if (env->insn_aux_data[i].ptr_type != PTR_TO_CTX)
+ if (env->insn_aux_data[i + delta].ptr_type != PTR_TO_CTX)
continue;
cnt = ops->convert_ctx_access(type, insn->dst_reg, insn->src_reg,
@@ -3263,8 +3348,7 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env)
return -EINVAL;
}
- new_prog = bpf_patch_insn_single(env->prog, i + delta, insn_buf,
- cnt);
+ new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt);
if (!new_prog)
return -ENOMEM;
@@ -3373,6 +3457,9 @@ skip_full_check:
free_states(env);
if (ret == 0)
+ sanitize_dead_code(env);
+
+ if (ret == 0)
/* program is valid, convert *(u32*)(ctx + off) accesses */
ret = convert_ctx_accesses(env);
generated by cgit v1.2.3 (git 2.25.1) at 2024-05-26 19:29:40 +0000