bpf: Unify resource leak checks

There are similar checks for covering locks, references, RCU read
sections and preempt_disable sections in 3 places in the verifer, i.e.
for tail calls, bpf_ld_[abs, ind], and exit path (for BPF_EXIT and
bpf_throw). Unify all of these into a common check_resource_leak
function to avoid code duplication.

Also update the error strings in selftests to the new ones in the same
change to ensure clean bisection.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20241103225940.1408302-3-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 34 insertions, 56 deletions

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 0844b4383ff3..ba800c7611e3 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -10352,6 +10352,34 @@ static int check_reference_leak(struct bpf_verifier_env *env, bool exception_exi
 	return refs_lingering ? -EINVAL : 0;
 }
 
+static int check_resource_leak(struct bpf_verifier_env *env, bool exception_exit, bool check_lock, const char *prefix)
+{
+	int err;
+
+	if (check_lock && env->cur_state->active_lock.ptr) {
+		verbose(env, "%s cannot be used inside bpf_spin_lock-ed region\n", prefix);
+		return -EINVAL;
+	}
+
+	err = check_reference_leak(env, exception_exit);
+	if (err) {
+		verbose(env, "%s would lead to reference leak\n", prefix);
+		return err;
+	}
+
+	if (check_lock && env->cur_state->active_rcu_lock) {
+		verbose(env, "%s cannot be used inside bpf_rcu_read_lock-ed region\n", prefix);
+		return -EINVAL;
+	}
+
+	if (check_lock && env->cur_state->active_preempt_lock) {
+		verbose(env, "%s cannot be used inside bpf_preempt_disable-ed region\n", prefix);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
 static int check_bpf_snprintf_call(struct bpf_verifier_env *env,
 				   struct bpf_reg_state *regs)
 {
@@ -10620,26 +10648,9 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
 
 	switch (func_id) {
 	case BPF_FUNC_tail_call:
-		if (env->cur_state->active_lock.ptr) {
-			verbose(env, "tail_call cannot be used inside bpf_spin_lock-ed region\n");
-			return -EINVAL;
-		}
-
-		err = check_reference_leak(env, false);
-		if (err) {
-			verbose(env, "tail_call would lead to reference leak\n");
+		err = check_resource_leak(env, false, true, "tail_call");
+		if (err)
 			return err;
-		}
-
-		if (env->cur_state->active_rcu_lock) {
-			verbose(env, "tail_call cannot be used inside bpf_rcu_read_lock-ed region\n");
-			return -EINVAL;
-		}
-
-		if (env->cur_state->active_preempt_lock) {
-			verbose(env, "tail_call cannot be used inside bpf_preempt_disable-ed region\n");
-			return -EINVAL;
-		}
 		break;
 	case BPF_FUNC_get_local_storage:
 		/* check that flags argument in get_local_storage(map, flags) is 0,
@@ -15801,26 +15812,9 @@ static int check_ld_abs(struct bpf_verifier_env *env, struct bpf_insn *insn)
 	 * gen_ld_abs() may terminate the program at runtime, leading to
 	 * reference leak.
 	 */
-	err = check_reference_leak(env, false);
-	if (err) {
-		verbose(env, "BPF_LD_[ABS|IND] cannot be mixed with socket references\n");
+	err = check_resource_leak(env, false, true, "BPF_LD_[ABS|IND]");
+	if (err)
 		return err;
-	}
-
-	if (env->cur_state->active_lock.ptr) {
-		verbose(env, "BPF_LD_[ABS|IND] cannot be used inside bpf_spin_lock-ed region\n");
-		return -EINVAL;
-	}
-
-	if (env->cur_state->active_rcu_lock) {
-		verbose(env, "BPF_LD_[ABS|IND] cannot be used inside bpf_rcu_read_lock-ed region\n");
-		return -EINVAL;
-	}
-
-	if (env->cur_state->active_preempt_lock) {
-		verbose(env, "BPF_LD_[ABS|IND] cannot be used inside bpf_preempt_disable-ed region\n");
-		return -EINVAL;
-	}
 
 	if (regs[ctx_reg].type != PTR_TO_CTX) {
 		verbose(env,
@@ -18606,30 +18600,14 @@ static int do_check(struct bpf_verifier_env *env)
 					return -EINVAL;
 				}
 process_bpf_exit_full:
-				if (env->cur_state->active_lock.ptr && !env->cur_state->curframe) {
-					verbose(env, "bpf_spin_unlock is missing\n");
-					return -EINVAL;
-				}
-
-				if (env->cur_state->active_rcu_lock && !env->cur_state->curframe) {
-					verbose(env, "bpf_rcu_read_unlock is missing\n");
-					return -EINVAL;
-				}
-
-				if (env->cur_state->active_preempt_lock && !env->cur_state->curframe) {
-					verbose(env, "%d bpf_preempt_enable%s missing\n",
-						env->cur_state->active_preempt_lock,
-						env->cur_state->active_preempt_lock == 1 ? " is" : "(s) are");
-					return -EINVAL;
-				}
-
 				/* We must do check_reference_leak here before
 				 * prepare_func_exit to handle the case when
 				 * state->curframe > 0, it may be a callback
 				 * function, for which reference_state must
 				 * match caller reference state when it exits.
 				 */
-				err = check_reference_leak(env, exception_exit);
+				err = check_resource_leak(env, exception_exit, !env->cur_state->curframe,
+							  "BPF_EXIT instruction");
 				if (err)
 					return err;