bpf: fix env->peak_states computation

Compute env->peak_states as a maximum value of sum of
env->explored_states and env->free_list size.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20250215110411.3236773-11-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Author: eddyz87

include/linux/bpf_verifier.h

@@ -772,6 +772,8 @@ struct bpf_verifier_env {
 	u32 peak_states;
 	/* longest register parentage chain walked for liveness marking */
 	u32 longest_mark_read_walk;
+	u32 free_list_size;
+	u32 explored_states_size;
 	bpfptr_t fd_array;
 
 	/* bit mask to keep track of whether a register has been accessed

kernel/bpf/verifier.c

@@ -1609,6 +1609,14 @@ static struct bpf_reference_state *find_lock_state(struct bpf_verifier_state *st
 	return NULL;
 }
 
+static void update_peak_states(struct bpf_verifier_env *env)
+{
+	u32 cur_states;
+
+	cur_states = env->explored_states_size + env->free_list_size;
+	env->peak_states = max(env->peak_states, cur_states);
+}
+
 static void free_func_state(struct bpf_func_state *state)
 {
 	if (!state)
@@ -1670,7 +1678,7 @@ static void maybe_free_verifier_state(struct bpf_verifier_env *env,
 		list_del(&sl->node);
 		free_verifier_state(&sl->state, false);
 		kfree(sl);
-		env->peak_states--;
+		env->free_list_size--;
 		sl = loop_entry_sl;
 	}
 }
@@ -18858,6 +18866,8 @@ static int is_state_visited(struct bpf_verifier_env *env, int insn_idx)
 			sl->in_free_list = true;
 			list_del(&sl->node);
 			list_add(&sl->node, &env->free_list);
+			env->free_list_size++;
+			env->explored_states_size--;
 			maybe_free_verifier_state(env, sl);
 		}
 	}
@@ -18884,7 +18894,8 @@ static int is_state_visited(struct bpf_verifier_env *env, int insn_idx)
 	if (!new_sl)
 		return -ENOMEM;
 	env->total_states++;
-	env->peak_states++;
+	env->explored_states_size++;
+	update_peak_states(env);
 	env->prev_jmps_processed = env->jmps_processed;
 	env->prev_insn_processed = env->insn_processed;