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Commit 4cb3d99c authored by Jiong Wang's avatar Jiong Wang Committed by Daniel Borkmann
Browse files

bpf: add faked "ending" subprog 



There are quite a few code snippet like the following in verifier:

       subprog_start = 0;
       if (env->subprog_cnt == cur_subprog + 1)
               subprog_end = insn_cnt;
       else
               subprog_end = env->subprog_info[cur_subprog + 1].start;

The reason is there is no marker in subprog_info array to tell the end of
it.

We could resolve this issue by introducing a faked "ending" subprog.
The special "ending" subprog is with "insn_cnt" as start offset, so it is
serving as the end mark whenever we iterate over all subprogs.

Signed-off-by: default avatarJiong Wang <jiong.wang@netronome.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parent 9c8105bd

kernel/bpf/verifier.c

+14 −20
Original line number Diff line number Diff line
@@ -769,7 +769,7 @@ static int add_subprog(struct bpf_verifier_env *env, int off) 
	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;

	}
@@ -810,15 +810,17 @@ static int check_subprogs(struct bpf_verifier_env *env) 
			return ret;

	}



	/* Add a fake 'exit' subprog which could simplify subprog iteration

	 * logic. 'subprog_cnt' should not be increased.

	 */

	subprog[env->subprog_cnt].start = insn_cnt;



	if (env->log.level > 1)

		for (i = 0; i < env->subprog_cnt; i++)

			verbose(env, "func#%d @%d\n", i, subprog[i].start);



	/* now check that all jumps are within the same subprog */

	subprog_start = 0;

	if (env->subprog_cnt == cur_subprog + 1)

		subprog_end = insn_cnt;

	else

	subprog_start = subprog[cur_subprog].start;

	subprog_end = subprog[cur_subprog + 1].start;

	for (i = 0; i < insn_cnt; i++) {

		u8 code = insn[i].code;
@@ -843,11 +845,9 @@ static int check_subprogs(struct bpf_verifier_env *env) 
				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 + 1)

				subprog_end = insn_cnt;

			else

			cur_subprog++;

			if (cur_subprog < env->subprog_cnt)

				subprog_end = subprog[cur_subprog + 1].start;

		}

	}
@@ -1502,7 +1502,6 @@ static int check_max_stack_depth(struct bpf_verifier_env *env) 
	int depth = 0, frame = 0, idx = 0, i = 0, subprog_end;

	struct bpf_subprog_info *subprog = env->subprog_info;

	struct bpf_insn *insn = env->prog->insnsi;

	int insn_cnt = env->prog->len;

	int ret_insn[MAX_CALL_FRAMES];

	int ret_prog[MAX_CALL_FRAMES];
@@ -1517,9 +1516,6 @@ static int check_max_stack_depth(struct bpf_verifier_env *env) 
		return -EACCES;

	}

continue_func:

	if (env->subprog_cnt == idx + 1)

		subprog_end = insn_cnt;

	else

	subprog_end = subprog[idx + 1].start;

	for (; i < subprog_end; i++) {

		if (insn[i].code != (BPF_JMP | BPF_CALL))
@@ -5141,7 +5137,8 @@ static void adjust_subprog_starts(struct bpf_verifier_env *env, u32 off, u32 len 


	if (len == 1)

		return;

	for (i = 0; i < env->subprog_cnt; i++) {

	/* NOTE: fake 'exit' subprog should be updated as well. */

	for (i = 0; i <= env->subprog_cnt; i++) {

		if (env->subprog_info[i].start < off)

			continue;

		env->subprog_info[i].start += len - 1;
@@ -5339,9 +5336,6 @@ static int jit_subprogs(struct bpf_verifier_env *env) 


	for (i = 0; i < env->subprog_cnt; i++) {

		subprog_start = subprog_end;

		if (env->subprog_cnt == i + 1)

			subprog_end = prog->len;

		else

		subprog_end = env->subprog_info[i + 1].start;



		len = subprog_end - subprog_start;