From: Jiong Wang <jiong.wang@netronome.com>
Date: Wed, 2 May 2018 16:17:17 -0400
Subject: bpf: unify main prog and subprog
Patch-mainline: v4.18-rc1
Git-commit: f910cefa32b6cdabc96b126bcfc46d8940b1dc45
References: bsc#1109837

Currently, verifier treat main prog and subprog differently. All subprogs
detected are kept in env->subprog_starts while main prog is not kept there.
Instead, main prog is implicitly defined as the prog start at 0.

There is actually no difference between main prog and subprog, it is better
to unify them, and register all progs detected into env->subprog_starts.

This could also help simplifying some code logic.

Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 include/linux/bpf_verifier.h |    2 -
 kernel/bpf/verifier.c        |   57 +++++++++++++++++++++++--------------------
 2 files changed, 32 insertions(+), 27 deletions(-)

--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -192,7 +192,7 @@ struct bpf_verifier_env {
 	bool seen_direct_write;
 	struct bpf_insn_aux_data *insn_aux_data; /* array of per-insn state */
 	struct bpf_verifier_log log;
-	u32 subprog_starts[BPF_MAX_SUBPROGS];
+	u32 subprog_starts[BPF_MAX_SUBPROGS + 1];
 	/* computes the stack depth of each bpf function */
 	u16 subprog_stack_depth[BPF_MAX_SUBPROGS + 1];
 	u32 subprog_cnt;
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -787,7 +787,7 @@ static int add_subprog(struct bpf_verifi
 	ret = find_subprog(env, off);
 	if (ret >= 0)
 		return 0;
-	if (env->subprog_cnt >= BPF_MAX_SUBPROGS) {
+	if (env->subprog_cnt > BPF_MAX_SUBPROGS) {
 		verbose(env, "too many subprograms\n");
 		return -E2BIG;
 	}
@@ -803,6 +803,11 @@ static int check_subprogs(struct bpf_ver
 	struct bpf_insn *insn = env->prog->insnsi;
 	int insn_cnt = env->prog->len;
 
+	/* Add entry function. */
+	ret = add_subprog(env, 0);
+	if (ret < 0)
+		return ret;
+
 	/* determine subprog starts. The end is one before the next starts */
 	for (i = 0; i < insn_cnt; i++) {
 		if (insn[i].code != (BPF_JMP | BPF_CALL))
@@ -828,10 +833,10 @@ static int check_subprogs(struct bpf_ver
 
 	/* now check that all jumps are within the same subprog */
 	subprog_start = 0;
-	if (env->subprog_cnt == cur_subprog)
+	if (env->subprog_cnt == cur_subprog + 1)
 		subprog_end = insn_cnt;
 	else
-		subprog_end = env->subprog_starts[cur_subprog++];
+		subprog_end = env->subprog_starts[cur_subprog + 1];
 	for (i = 0; i < insn_cnt; i++) {
 		u8 code = insn[i].code;
 
@@ -855,11 +860,13 @@ next:
 				verbose(env, "last insn is not an exit or jmp\n");
 				return -EINVAL;
 			}
+			cur_subprog++;
 			subprog_start = subprog_end;
-			if (env->subprog_cnt == cur_subprog)
+			if (env->subprog_cnt == cur_subprog + 1)
 				subprog_end = insn_cnt;
 			else
-				subprog_end = env->subprog_starts[cur_subprog++];
+				subprog_end =
+					env->subprog_starts[cur_subprog + 1];
 		}
 	}
 	return 0;
@@ -1575,10 +1582,10 @@ process_func:
 		return -EACCES;
 	}
 continue_func:
-	if (env->subprog_cnt == subprog)
+	if (env->subprog_cnt == subprog + 1)
 		subprog_end = insn_cnt;
 	else
-		subprog_end = env->subprog_starts[subprog];
+		subprog_end = env->subprog_starts[subprog + 1];
 	for (; i < subprog_end; i++) {
 		if (insn[i].code != (BPF_JMP | BPF_CALL))
 			continue;
@@ -1596,7 +1603,6 @@ continue_func:
 				  i);
 			return -EFAULT;
 		}
-		subprog++;
 		frame++;
 		if (frame >= MAX_CALL_FRAMES) {
 			WARN_ONCE(1, "verifier bug. Call stack is too deep\n");
@@ -1628,7 +1634,6 @@ static int get_callee_stack_depth(struct
 			  start);
 		return -EFAULT;
 	}
-	subprog++;
 	return env->subprog_stack_depth[subprog];
 }
 #endif
@@ -2137,7 +2142,7 @@ static int check_map_func_compatibility(
 	case BPF_FUNC_tail_call:
 		if (map->map_type != BPF_MAP_TYPE_PROG_ARRAY)
 			goto error;
-		if (env->subprog_cnt) {
+		if (env->subprog_cnt > 1) {
 			verbose(env, "tail_calls are not allowed in programs with bpf-to-bpf calls\n");
 			return -EINVAL;
 		}
@@ -2310,7 +2315,7 @@ static int check_func_call(struct bpf_ve
 			/* remember the callsite, it will be used by bpf_exit */
 			*insn_idx /* callsite */,
 			state->curframe + 1 /* frameno within this callchain */,
-			subprog + 1 /* subprog number within this prog */);
+			subprog /* subprog number within this prog */);
 
 	/* copy r1 - r5 args that callee can access */
 	for (i = BPF_REG_1; i <= BPF_REG_5; i++)
@@ -3903,7 +3908,7 @@ static int check_ld_abs(struct bpf_verif
 		return -EINVAL;
 	}
 
-	if (env->subprog_cnt) {
+	if (env->subprog_cnt > 1) {
 		/* when program has LD_ABS insn JITs and interpreter assume
 		 * that r1 == ctx == skb which is not the case for callees
 		 * that can have arbitrary arguments. It's problematic
@@ -4932,11 +4937,11 @@ process_bpf_exit:
 
 	verbose(env, "processed %d insns (limit %d), stack depth ",
 		insn_processed, BPF_COMPLEXITY_LIMIT_INSNS);
-	for (i = 0; i < env->subprog_cnt + 1; i++) {
+	for (i = 0; i < env->subprog_cnt; i++) {
 		u32 depth = env->subprog_stack_depth[i];
 
 		verbose(env, "%d", depth);
-		if (i + 1 < env->subprog_cnt + 1)
+		if (i + 1 < env->subprog_cnt)
 			verbose(env, "+");
 	}
 	verbose(env, "\n");
@@ -5342,7 +5347,7 @@ static int jit_subprogs(struct bpf_verif
 	void *old_bpf_func;
 	int err = -ENOMEM;
 
-	if (env->subprog_cnt == 0)
+	if (env->subprog_cnt <= 1)
 		return 0;
 
 	for (i = 0, insn = prog->insnsi; i < prog->len; i++, insn++) {
@@ -5358,7 +5363,7 @@ static int jit_subprogs(struct bpf_verif
 		/* temporarily remember subprog id inside insn instead of
 		 * aux_data, since next loop will split up all insns into funcs
 		 */
-		insn->off = subprog + 1;
+		insn->off = subprog;
 		/* remember original imm in case JIT fails and fallback
 		 * to interpreter will be needed
 		 */
@@ -5367,16 +5372,16 @@ static int jit_subprogs(struct bpf_verif
 		insn->imm = 1;
 	}
 
-	func = kzalloc(sizeof(prog) * (env->subprog_cnt + 1), GFP_KERNEL);
+	func = kzalloc(sizeof(prog) * env->subprog_cnt, GFP_KERNEL);
 	if (!func)
 		return -ENOMEM;
 
-	for (i = 0; i <= env->subprog_cnt; i++) {
+	for (i = 0; i < env->subprog_cnt; i++) {
 		subprog_start = subprog_end;
-		if (env->subprog_cnt == i)
+		if (env->subprog_cnt == i + 1)
 			subprog_end = prog->len;
 		else
-			subprog_end = env->subprog_starts[i];
+			subprog_end = env->subprog_starts[i + 1];
 
 		len = subprog_end - subprog_start;
 		func[i] = bpf_prog_alloc(bpf_prog_size(len), GFP_USER);
@@ -5406,7 +5411,7 @@ static int jit_subprogs(struct bpf_verif
 	 * now populate all bpf_calls with correct addresses and
 	 * run last pass of JIT
 	 */
-	for (i = 0; i <= env->subprog_cnt; i++) {
+	for (i = 0; i < env->subprog_cnt; i++) {
 		insn = func[i]->insnsi;
 		for (j = 0; j < func[i]->len; j++, insn++) {
 			if (insn->code != (BPF_JMP | BPF_CALL) ||
@@ -5419,7 +5424,7 @@ static int jit_subprogs(struct bpf_verif
 				__bpf_call_base;
 		}
 	}
-	for (i = 0; i <= env->subprog_cnt; i++) {
+	for (i = 0; i < env->subprog_cnt; i++) {
 		old_bpf_func = func[i]->bpf_func;
 		tmp = bpf_int_jit_compile(func[i]);
 		if (tmp != func[i] || func[i]->bpf_func != old_bpf_func) {
@@ -5433,7 +5438,7 @@ static int jit_subprogs(struct bpf_verif
 	/* finally lock prog and jit images for all functions and
 	 * populate kallsysm
 	 */
-	for (i = 0; i <= env->subprog_cnt; i++) {
+	for (i = 0; i < env->subprog_cnt; i++) {
 		bpf_prog_lock_ro(func[i]);
 		bpf_prog_kallsyms_add(func[i]);
 	}
@@ -5450,7 +5455,7 @@ static int jit_subprogs(struct bpf_verif
 			continue;
 		insn->off = env->insn_aux_data[i].call_imm;
 		subprog = find_subprog(env, i + insn->off + 1);
-		addr  = (unsigned long)func[subprog + 1]->bpf_func;
+		addr  = (unsigned long)func[subprog]->bpf_func;
 		addr &= PAGE_MASK;
 		insn->imm = (u64 (*)(u64, u64, u64, u64, u64))
 			    addr - __bpf_call_base;
@@ -5459,10 +5464,10 @@ static int jit_subprogs(struct bpf_verif
 	prog->jited = 1;
 	prog->bpf_func = func[0]->bpf_func;
 	prog->aux->func = func;
-	prog->aux->func_cnt = env->subprog_cnt + 1;
+	prog->aux->func_cnt = env->subprog_cnt;
 	return 0;
 out_free:
-	for (i = 0; i <= env->subprog_cnt; i++)
+	for (i = 0; i < env->subprog_cnt; i++)
 		if (func[i])
 			bpf_jit_free(func[i]);
 	kfree(func);