bpf: starting_state parameter for __mark_chain_precision()

Allow `mark_chain_precision()` to run from an arbitrary starting state
by replacing direct references to `env->cur_state` with a parameter.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20250611200836.4135542-4-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index ebb98a78c91970fa6c60391b0af3fac758a4761f..cca8858c3caafd26f8ea303c4a4de50bb0104a84 100644 (file)
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -4677,12 +4677,13 @@ static void mark_all_scalars_imprecise(struct bpf_verifier_env *env, struct bpf_
  * mark_all_scalars_imprecise() to hopefully get more permissive and generic
  * finalized states which help in short circuiting more future states.
  */
-static int __mark_chain_precision(struct bpf_verifier_env *env, int regno)
+static int __mark_chain_precision(struct bpf_verifier_env *env,
+                                 struct bpf_verifier_state *starting_state, int regno)
 {
+       struct bpf_verifier_state *st = starting_state;
        struct backtrack_state *bt = &env->bt;
-       struct bpf_verifier_state *st = env->cur_state;
        int first_idx = st->first_insn_idx;
-       int last_idx = env->insn_idx;
+       int last_idx = starting_state->insn_idx;
        int subseq_idx = -1;
        struct bpf_func_state *func;
        struct bpf_reg_state *reg;
@@ -4693,7 +4694,7 @@ static int __mark_chain_precision(struct bpf_verifier_env *env, int regno)
                return 0;
 
        /* set frame number from which we are starting to backtrack */
-       bt_init(bt, env->cur_state->curframe);
+       bt_init(bt, starting_state->curframe);
 
        /* Do sanity checks against current state of register and/or stack
         * slot, but don't set precise flag in current state, as precision
@@ -4757,7 +4758,7 @@ static int __mark_chain_precision(struct bpf_verifier_env *env, int regno)
                                err = backtrack_insn(env, i, subseq_idx, hist, bt);
                        }
                        if (err == -ENOTSUPP) {
-                               mark_all_scalars_precise(env, env->cur_state);
+                               mark_all_scalars_precise(env, starting_state);
                                bt_reset(bt);
                                return 0;
                        } else if (err) {
@@ -4845,7 +4846,7 @@ static int __mark_chain_precision(struct bpf_verifier_env *env, int regno)
         * fallback to marking all precise
         */
        if (!bt_empty(bt)) {
-               mark_all_scalars_precise(env, env->cur_state);
+               mark_all_scalars_precise(env, starting_state);
                bt_reset(bt);
        }
 
@@ -4854,15 +4855,16 @@ static int __mark_chain_precision(struct bpf_verifier_env *env, int regno)
 
 int mark_chain_precision(struct bpf_verifier_env *env, int regno)
 {
-       return __mark_chain_precision(env, regno);
+       return __mark_chain_precision(env, env->cur_state, regno);
 }
 
 /* mark_chain_precision_batch() assumes that env->bt is set in the caller to
  * desired reg and stack masks across all relevant frames
  */
-static int mark_chain_precision_batch(struct bpf_verifier_env *env)
+static int mark_chain_precision_batch(struct bpf_verifier_env *env,
+                                     struct bpf_verifier_state *starting_state)
 {
-       return __mark_chain_precision(env, -1);
+       return __mark_chain_precision(env, starting_state, -1);
 }
 
 static bool is_spillable_regtype(enum bpf_reg_type type)
@@ -9515,7 +9517,7 @@ static int get_constant_map_key(struct bpf_verifier_env *env,
         * to prevent pruning on it.
         */
        bt_set_frame_slot(&env->bt, key->frameno, spi);
-       err = mark_chain_precision_batch(env);
+       err = mark_chain_precision_batch(env, env->cur_state);
        if (err < 0)
                return err;
 
@@ -18939,7 +18941,7 @@ static int propagate_precision(struct bpf_verifier_env *env,
                        verbose(env, "\n");
        }
 
-       err = mark_chain_precision_batch(env);
+       err = mark_chain_precision_batch(env, env->cur_state);
        if (err < 0)
                return err;