bpf: Make BPF_PROG_RUN_ARRAY return -err instead of allow boolean

Right now BPF_PROG_RUN_ARRAY and related macros return 1 or 0
for whether the prog array allows or rejects whatever is being
hooked. The caller of these macros then return -EPERM or continue
processing based on thw macro's return value. Unforunately this is
inflexible, since -EPERM is the only err that can be returned.

This patch should be a no-op; it prepares for the next patch. The
returning of the -EPERM is moved to inside the macros, so the outer
functions are directly returning what the macros returned if they
are non-zero.

Signed-off-by: YiFei Zhu <zhuyifei@google.com>
Reviewed-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/r/788abcdca55886d1f43274c918eaa9f792a9f33b.1639619851.git.zhuyifei@google.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Author: zhuyifei1999

include/linux/bpf.h

@@ -1277,7 +1277,7 @@ static inline void bpf_reset_run_ctx(struct bpf_run_ctx *old_ctx)
 
 typedef u32 (*bpf_prog_run_fn)(const struct bpf_prog *prog, const void *ctx);
 
-static __always_inline u32
+static __always_inline int
 BPF_PROG_RUN_ARRAY_CG_FLAGS(const struct bpf_prog_array __rcu *array_rcu,
 			    const void *ctx, bpf_prog_run_fn run_prog,
 			    u32 *ret_flags)
@@ -1287,7 +1287,7 @@ BPF_PROG_RUN_ARRAY_CG_FLAGS(const struct bpf_prog_array __rcu *array_rcu,
 	const struct bpf_prog_array *array;
 	struct bpf_run_ctx *old_run_ctx;
 	struct bpf_cg_run_ctx run_ctx;
-	u32 ret = 1;
+	int ret = 0;
 	u32 func_ret;
 
 	migrate_disable();
@@ -1298,7 +1298,8 @@ BPF_PROG_RUN_ARRAY_CG_FLAGS(const struct bpf_prog_array __rcu *array_rcu,
 	while ((prog = READ_ONCE(item->prog))) {
 		run_ctx.prog_item = item;
 		func_ret = run_prog(prog, ctx);
-		ret &= (func_ret & 1);
+		if (!(func_ret & 1))
+			ret = -EPERM;
 		*(ret_flags) |= (func_ret >> 1);
 		item++;
 	}
@@ -1308,7 +1309,7 @@ BPF_PROG_RUN_ARRAY_CG_FLAGS(const struct bpf_prog_array __rcu *array_rcu,
 	return ret;
 }
 
-static __always_inline u32
+static __always_inline int
 BPF_PROG_RUN_ARRAY_CG(const struct bpf_prog_array __rcu *array_rcu,
 		      const void *ctx, bpf_prog_run_fn run_prog)
 {
@@ -1317,7 +1318,7 @@ BPF_PROG_RUN_ARRAY_CG(const struct bpf_prog_array __rcu *array_rcu,
 	const struct bpf_prog_array *array;
 	struct bpf_run_ctx *old_run_ctx;
 	struct bpf_cg_run_ctx run_ctx;
-	u32 ret = 1;
+	int ret = 0;
 
 	migrate_disable();
 	rcu_read_lock();
@@ -1326,7 +1327,8 @@ BPF_PROG_RUN_ARRAY_CG(const struct bpf_prog_array __rcu *array_rcu,
 	old_run_ctx = bpf_set_run_ctx(&run_ctx.run_ctx);
 	while ((prog = READ_ONCE(item->prog))) {
 		run_ctx.prog_item = item;
-		ret &= run_prog(prog, ctx);
+		if (!run_prog(prog, ctx))
+			ret = -EPERM;
 		item++;
 	}
 	bpf_reset_run_ctx(old_run_ctx);
@@ -1394,7 +1396,7 @@ BPF_PROG_RUN_ARRAY(const struct bpf_prog_array __rcu *array_rcu,
 		u32 _ret;				\
 		_ret = BPF_PROG_RUN_ARRAY_CG_FLAGS(array, ctx, func, &_flags); \
 		_cn = _flags & BPF_RET_SET_CN;		\
-		if (_ret)				\
+		if (!_ret)				\
 			_ret = (_cn ? NET_XMIT_CN : NET_XMIT_SUCCESS);	\
 		else					\
 			_ret = (_cn ? NET_XMIT_DROP : -EPERM);		\

kernel/bpf/cgroup.c

@@ -1080,7 +1080,6 @@ int __cgroup_bpf_run_filter_skb(struct sock *sk,
 	} else {
 		ret = BPF_PROG_RUN_ARRAY_CG(cgrp->bpf.effective[atype], skb,
 					    __bpf_prog_run_save_cb);
-		ret = (ret == 1 ? 0 : -EPERM);
 	}
 	bpf_restore_data_end(skb, saved_data_end);
 	__skb_pull(skb, offset);
@@ -1107,10 +1106,9 @@ int __cgroup_bpf_run_filter_sk(struct sock *sk,
 			       enum cgroup_bpf_attach_type atype)
 {
 	struct cgroup *cgrp = sock_cgroup_ptr(&sk->sk_cgrp_data);
-	int ret;
 
-	ret = BPF_PROG_RUN_ARRAY_CG(cgrp->bpf.effective[atype], sk, bpf_prog_run);
-	return ret == 1 ? 0 : -EPERM;
+	return BPF_PROG_RUN_ARRAY_CG(cgrp->bpf.effective[atype], sk,
+				     bpf_prog_run);
 }
 EXPORT_SYMBOL(__cgroup_bpf_run_filter_sk);
 
@@ -1142,7 +1140,6 @@ int __cgroup_bpf_run_filter_sock_addr(struct sock *sk,
 	};
 	struct sockaddr_storage unspec;
 	struct cgroup *cgrp;
-	int ret;
 
 	/* Check socket family since not all sockets represent network
 	 * endpoint (e.g. AF_UNIX).
@@ -1156,10 +1153,8 @@ int __cgroup_bpf_run_filter_sock_addr(struct sock *sk,
 	}
 
 	cgrp = sock_cgroup_ptr(&sk->sk_cgrp_data);
-	ret = BPF_PROG_RUN_ARRAY_CG_FLAGS(cgrp->bpf.effective[atype], &ctx,
-				          bpf_prog_run, flags);
-
-	return ret == 1 ? 0 : -EPERM;
+	return BPF_PROG_RUN_ARRAY_CG_FLAGS(cgrp->bpf.effective[atype], &ctx,
+					   bpf_prog_run, flags);
 }
 EXPORT_SYMBOL(__cgroup_bpf_run_filter_sock_addr);
 
@@ -1184,11 +1179,9 @@ int __cgroup_bpf_run_filter_sock_ops(struct sock *sk,
 				     enum cgroup_bpf_attach_type atype)
 {
 	struct cgroup *cgrp = sock_cgroup_ptr(&sk->sk_cgrp_data);
-	int ret;
 
-	ret = BPF_PROG_RUN_ARRAY_CG(cgrp->bpf.effective[atype], sock_ops,
-				    bpf_prog_run);
-	return ret == 1 ? 0 : -EPERM;
+	return BPF_PROG_RUN_ARRAY_CG(cgrp->bpf.effective[atype], sock_ops,
+				     bpf_prog_run);
 }
 EXPORT_SYMBOL(__cgroup_bpf_run_filter_sock_ops);
 
@@ -1201,15 +1194,15 @@ int __cgroup_bpf_check_dev_permission(short dev_type, u32 major, u32 minor,
 		.major = major,
 		.minor = minor,
 	};
-	int allow;
+	int ret;
 
 	rcu_read_lock();
 	cgrp = task_dfl_cgroup(current);
-	allow = BPF_PROG_RUN_ARRAY_CG(cgrp->bpf.effective[atype], &ctx,
-				      bpf_prog_run);
+	ret = BPF_PROG_RUN_ARRAY_CG(cgrp->bpf.effective[atype], &ctx,
+				    bpf_prog_run);
 	rcu_read_unlock();
 
-	return !allow;
+	return ret;
 }
 
 static const struct bpf_func_proto *
@@ -1350,7 +1343,7 @@ int __cgroup_bpf_run_filter_sysctl(struct ctl_table_header *head,
 		kfree(ctx.new_val);
 	}
 
-	return ret == 1 ? 0 : -EPERM;
+	return ret;
 }
 
 #ifdef CONFIG_NET
@@ -1455,10 +1448,8 @@ int __cgroup_bpf_run_filter_setsockopt(struct sock *sk, int *level,
 				    &ctx, bpf_prog_run);
 	release_sock(sk);
 
-	if (!ret) {
-		ret = -EPERM;
+	if (ret)
 		goto out;
-	}
 
 	if (ctx.optlen == -1) {
 		/* optlen set to -1, bypass kernel */
@@ -1565,10 +1556,8 @@ int __cgroup_bpf_run_filter_getsockopt(struct sock *sk, int level,
 				    &ctx, bpf_prog_run);
 	release_sock(sk);
 
-	if (!ret) {
-		ret = -EPERM;
+	if (ret)
 		goto out;
-	}
 
 	if (ctx.optlen > max_optlen || ctx.optlen < 0) {
 		ret = -EFAULT;
@@ -1624,8 +1613,8 @@ int __cgroup_bpf_run_filter_getsockopt_kern(struct sock *sk, int level,
 
 	ret = BPF_PROG_RUN_ARRAY_CG(cgrp->bpf.effective[CGROUP_GETSOCKOPT],
 				    &ctx, bpf_prog_run);
-	if (!ret)
-		return -EPERM;
+	if (ret)
+		return ret;
 
 	if (ctx.optlen > *optlen)
 		return -EFAULT;

security/device_cgroup.c

@@ -838,7 +838,7 @@ int devcgroup_check_permission(short type, u32 major, u32 minor, short access)
 	int rc = BPF_CGROUP_RUN_PROG_DEVICE_CGROUP(type, major, minor, access);
 
 	if (rc)
-		return -EPERM;
+		return rc;
 
 	#ifdef CONFIG_CGROUP_DEVICE
 	return devcgroup_legacy_check_permission(type, major, minor, access);