[01/12] bpf: move {prev_,}insn_idx into verifier env

Message ID 1549862631-24152-2-git-send-email-tyhicks@canonical.com
State New
Headers show
Series
  • Multiple BPF security issues
Related show

Commit Message

Tyler Hicks Feb. 11, 2019, 5:23 a.m.
From: Daniel Borkmann <daniel@iogearbox.net>

Move prev_insn_idx and insn_idx from the do_check() function into
the verifier environment, so they can be read inside the various
helper functions for handling the instructions. It's easier to put
this into the environment rather than changing all call-sites only
to pass it along. insn_idx is useful in particular since this later
on allows to hold state in env->insn_aux_data[env->insn_idx].

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

CVE-2019-7308

(backported from commit c08435ec7f2bc8f4109401f696fd55159b4b40cb)
[tyhicks: Backport around missing verbose logging message]
[tyhicks: Backport around minor whitespace difference]
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
---
 include/linux/bpf_verifier.h |  2 ++
 kernel/bpf/verifier.c        | 75 ++++++++++++++++++++++----------------------
 2 files changed, 40 insertions(+), 37 deletions(-)

Patch

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 1fd6fa822d2c..b1587ffdea7b 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -186,6 +186,8 @@  struct bpf_subprog_info {
  * one verifier_env per bpf_check() call
  */
 struct bpf_verifier_env {
+	u32 insn_idx;
+	u32 prev_insn_idx;
 	struct bpf_prog *prog;		/* eBPF program being verified */
 	const struct bpf_verifier_ops *ops;
 	struct bpf_verifier_stack_elem *head; /* stack of verifier states to be processed */
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index d565ec6af97c..00d51e3b4890 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -4703,7 +4703,6 @@  static int do_check(struct bpf_verifier_env *env)
 	struct bpf_insn *insns = env->prog->insnsi;
 	struct bpf_reg_state *regs;
 	int insn_cnt = env->prog->len, i;
-	int insn_idx, prev_insn_idx = 0;
 	int insn_processed = 0;
 	bool do_print_state = false;
 
@@ -4722,19 +4721,19 @@  static int do_check(struct bpf_verifier_env *env)
 			BPF_MAIN_FUNC /* callsite */,
 			0 /* frameno */,
 			0 /* subprogno, zero == main subprog */);
-	insn_idx = 0;
+
 	for (;;) {
 		struct bpf_insn *insn;
 		u8 class;
 		int err;
 
-		if (insn_idx >= insn_cnt) {
+		if (env->insn_idx >= insn_cnt) {
 			verbose(env, "invalid insn idx %d insn_cnt %d\n",
-				insn_idx, insn_cnt);
+				env->insn_idx, insn_cnt);
 			return -EFAULT;
 		}
 
-		insn = &insns[insn_idx];
+		insn = &insns[env->insn_idx];
 		class = BPF_CLASS(insn->code);
 
 		if (++insn_processed > BPF_COMPLEXITY_LIMIT_INSNS) {
@@ -4744,7 +4743,7 @@  static int do_check(struct bpf_verifier_env *env)
 			return -E2BIG;
 		}
 
-		err = is_state_visited(env, insn_idx);
+		err = is_state_visited(env, env->insn_idx);
 		if (err < 0)
 			return err;
 		if (err == 1) {
@@ -4752,9 +4751,9 @@  static int do_check(struct bpf_verifier_env *env)
 			if (env->log.level) {
 				if (do_print_state)
 					verbose(env, "\nfrom %d to %d: safe\n",
-						prev_insn_idx, insn_idx);
+						env->prev_insn_idx, env->insn_idx);
 				else
-					verbose(env, "%d: safe\n", insn_idx);
+					verbose(env, "%d: safe\n", env->insn_idx);
 			}
 			goto process_bpf_exit;
 		}
@@ -4764,10 +4763,10 @@  static int do_check(struct bpf_verifier_env *env)
 
 		if (env->log.level > 1 || (env->log.level && do_print_state)) {
 			if (env->log.level > 1)
-				verbose(env, "%d:", insn_idx);
+				verbose(env, "%d:", env->insn_idx);
 			else
 				verbose(env, "\nfrom %d to %d:",
-					prev_insn_idx, insn_idx);
+					env->prev_insn_idx, env->insn_idx);
 			print_verifier_state(env, state->frame[state->curframe]);
 			do_print_state = false;
 		}
@@ -4778,19 +4777,20 @@  static int do_check(struct bpf_verifier_env *env)
 				.private_data	= env,
 			};
 
-			verbose(env, "%d: ", insn_idx);
+			verbose(env, "%d: ", env->insn_idx);
 			print_bpf_insn(&cbs, insn, env->allow_ptr_leaks);
 		}
 
 		if (bpf_prog_is_dev_bound(env->prog->aux)) {
-			err = bpf_prog_offload_verify_insn(env, insn_idx,
-							   prev_insn_idx);
+			err = bpf_prog_offload_verify_insn(env, env->insn_idx,
+							   env->prev_insn_idx);
 			if (err)
 				return err;
 		}
 
 		regs = cur_regs(env);
-		env->insn_aux_data[insn_idx].seen = true;
+		env->insn_aux_data[env->insn_idx].seen = true;
+
 		if (class == BPF_ALU || class == BPF_ALU64) {
 			err = check_alu_op(env, insn);
 			if (err)
@@ -4815,13 +4815,13 @@  static int do_check(struct bpf_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_idx, insn->src_reg, insn->off,
-					       BPF_SIZE(insn->code), BPF_READ,
-					       insn->dst_reg, false);
+			err = check_mem_access(env, env->insn_idx, insn->src_reg,
+					       insn->off, BPF_SIZE(insn->code),
+					       BPF_READ, insn->dst_reg, false);
 			if (err)
 				return err;
 
-			prev_src_type = &env->insn_aux_data[insn_idx].ptr_type;
+			prev_src_type = &env->insn_aux_data[env->insn_idx].ptr_type;
 
 			if (*prev_src_type == NOT_INIT) {
 				/* saw a valid insn
@@ -4848,10 +4848,10 @@  static int do_check(struct bpf_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_idx, insn);
+				err = check_xadd(env, env->insn_idx, insn);
 				if (err)
 					return err;
-				insn_idx++;
+				env->insn_idx++;
 				continue;
 			}
 
@@ -4867,13 +4867,13 @@  static int do_check(struct bpf_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_idx, insn->dst_reg, insn->off,
-					       BPF_SIZE(insn->code), BPF_WRITE,
-					       insn->src_reg, false);
+			err = check_mem_access(env, env->insn_idx, insn->dst_reg,
+					       insn->off, BPF_SIZE(insn->code),
+					       BPF_WRITE, insn->src_reg, false);
 			if (err)
 				return err;
 
-			prev_dst_type = &env->insn_aux_data[insn_idx].ptr_type;
+			prev_dst_type = &env->insn_aux_data[env->insn_idx].ptr_type;
 
 			if (*prev_dst_type == NOT_INIT) {
 				*prev_dst_type = dst_reg_type;
@@ -4902,9 +4902,9 @@  static int do_check(struct bpf_verifier_env *env)
 			}
 
 			/* check that memory (dst_reg + off) is writeable */
-			err = check_mem_access(env, insn_idx, insn->dst_reg, insn->off,
-					       BPF_SIZE(insn->code), BPF_WRITE,
-					       -1, false);
+			err = check_mem_access(env, env->insn_idx, insn->dst_reg,
+					       insn->off, BPF_SIZE(insn->code),
+					       BPF_WRITE, -1, false);
 			if (err)
 				return err;
 
@@ -4922,9 +4922,9 @@  static int do_check(struct bpf_verifier_env *env)
 				}
 
 				if (insn->src_reg == BPF_PSEUDO_CALL)
-					err = check_func_call(env, insn, &insn_idx);
+					err = check_func_call(env, insn, &env->insn_idx);
 				else
-					err = check_helper_call(env, insn->imm, insn_idx);
+					err = check_helper_call(env, insn->imm, env->insn_idx);
 				if (err)
 					return err;
 
@@ -4937,7 +4937,7 @@  static int do_check(struct bpf_verifier_env *env)
 					return -EINVAL;
 				}
 
-				insn_idx += insn->off + 1;
+				env->insn_idx += insn->off + 1;
 				continue;
 
 			} else if (opcode == BPF_EXIT) {
@@ -4951,8 +4951,8 @@  static int do_check(struct bpf_verifier_env *env)
 
 				if (state->curframe) {
 					/* exit from nested function */
-					prev_insn_idx = insn_idx;
-					err = prepare_func_exit(env, &insn_idx);
+					env->prev_insn_idx = env->insn_idx;
+					err = prepare_func_exit(env, &env->insn_idx);
 					if (err)
 						return err;
 					do_print_state = true;
@@ -4978,7 +4978,8 @@  static int do_check(struct bpf_verifier_env *env)
 				if (err)
 					return err;
 process_bpf_exit:
-				err = pop_stack(env, &prev_insn_idx, &insn_idx);
+				err = pop_stack(env, &env->prev_insn_idx,
+						&env->insn_idx);
 				if (err < 0) {
 					if (err != -ENOENT)
 						return err;
@@ -4988,7 +4989,7 @@  static int do_check(struct bpf_verifier_env *env)
 					continue;
 				}
 			} else {
-				err = check_cond_jmp_op(env, insn, &insn_idx);
+				err = check_cond_jmp_op(env, insn, &env->insn_idx);
 				if (err)
 					return err;
 			}
@@ -5005,8 +5006,8 @@  static int do_check(struct bpf_verifier_env *env)
 				if (err)
 					return err;
 
-				insn_idx++;
-				env->insn_aux_data[insn_idx].seen = true;
+				env->insn_idx++;
+				env->insn_aux_data[env->insn_idx].seen = true;
 			} else {
 				verbose(env, "invalid BPF_LD mode\n");
 				return -EINVAL;
@@ -5016,7 +5017,7 @@  static int do_check(struct bpf_verifier_env *env)
 			return -EINVAL;
 		}
 
-		insn_idx++;
+		env->insn_idx++;
 	}
 
 	verbose(env, "processed %d insns (limit %d), stack depth ",