bpf: Move rcu lock management out of BPF_PROG_RUN routines

Commit 7d08c2c91171 ("bpf: Refactor BPF_PROG_RUN_ARRAY family of macros
into functions") switched a bunch of BPF_PROG_RUN macros to inline
routines. This changed the semantic a bit. Due to arguments expansion
of macros, it used to be:

	rcu_read_lock();
	array = rcu_dereference(cgrp->bpf.effective[atype]);
	...

Now, with with inline routines, we have:
	array_rcu = rcu_dereference(cgrp->bpf.effective[atype]);
	/* array_rcu can be kfree'd here */
	rcu_read_lock();
	array = rcu_dereference(array_rcu);

I'm assuming in practice rcu subsystem isn't fast enough to trigger
this but let's use rcu API properly.

Also, rename to lower caps to not confuse with macros. Additionally,
drop and expand BPF_PROG_CGROUP_INET_EGRESS_RUN_ARRAY.

See [1] for more context.

  [1] https://lore.kernel.org/bpf/CAKH8qBs60fOinFdxiiQikK_q0EcVxGvNTQoWvHLEUGbgcj1UYg@mail.gmail.com/T/#u

v2
- keep rcu locks inside by passing cgroup_bpf

Fixes: 7d08c2c91171 ("bpf: Refactor BPF_PROG_RUN_ARRAY family of macros into functions")
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20220414161233.170780-1-sdf@google.com

1 files changed, 107 insertions, 17 deletions

diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index 128028efda64..0cb6211fcb58 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -22,6 +22,72 @@
 DEFINE_STATIC_KEY_ARRAY_FALSE(cgroup_bpf_enabled_key, MAX_CGROUP_BPF_ATTACH_TYPE);
 EXPORT_SYMBOL(cgroup_bpf_enabled_key);
 
+/* __always_inline is necessary to prevent indirect call through run_prog
+ * function pointer.
+ */
+static __always_inline int
+bpf_prog_run_array_cg_flags(const struct cgroup_bpf *cgrp,
+			    enum cgroup_bpf_attach_type atype,
+			    const void *ctx, bpf_prog_run_fn run_prog,
+			    int retval, u32 *ret_flags)
+{
+	const struct bpf_prog_array_item *item;
+	const struct bpf_prog *prog;
+	const struct bpf_prog_array *array;
+	struct bpf_run_ctx *old_run_ctx;
+	struct bpf_cg_run_ctx run_ctx;
+	u32 func_ret;
+
+	run_ctx.retval = retval;
+	migrate_disable();
+	rcu_read_lock();
+	array = rcu_dereference(cgrp->effective[atype]);
+	item = &array->items[0];
+	old_run_ctx = bpf_set_run_ctx(&run_ctx.run_ctx);
+	while ((prog = READ_ONCE(item->prog))) {
+		run_ctx.prog_item = item;
+		func_ret = run_prog(prog, ctx);
+		if (!(func_ret & 1) && !IS_ERR_VALUE((long)run_ctx.retval))
+			run_ctx.retval = -EPERM;
+		*(ret_flags) |= (func_ret >> 1);
+		item++;
+	}
+	bpf_reset_run_ctx(old_run_ctx);
+	rcu_read_unlock();
+	migrate_enable();
+	return run_ctx.retval;
+}
+
+static __always_inline int
+bpf_prog_run_array_cg(const struct cgroup_bpf *cgrp,
+		      enum cgroup_bpf_attach_type atype,
+		      const void *ctx, bpf_prog_run_fn run_prog,
+		      int retval)
+{
+	const struct bpf_prog_array_item *item;
+	const struct bpf_prog *prog;
+	const struct bpf_prog_array *array;
+	struct bpf_run_ctx *old_run_ctx;
+	struct bpf_cg_run_ctx run_ctx;
+
+	run_ctx.retval = retval;
+	migrate_disable();
+	rcu_read_lock();
+	array = rcu_dereference(cgrp->effective[atype]);
+	item = &array->items[0];
+	old_run_ctx = bpf_set_run_ctx(&run_ctx.run_ctx);
+	while ((prog = READ_ONCE(item->prog))) {
+		run_ctx.prog_item = item;
+		if (!run_prog(prog, ctx) && !IS_ERR_VALUE((long)run_ctx.retval))
+			run_ctx.retval = -EPERM;
+		item++;
+	}
+	bpf_reset_run_ctx(old_run_ctx);
+	rcu_read_unlock();
+	migrate_enable();
+	return run_ctx.retval;
+}
+
 void cgroup_bpf_offline(struct cgroup *cgrp)
 {
 	cgroup_get(cgrp);
@@ -1075,11 +1141,38 @@ int __cgroup_bpf_run_filter_skb(struct sock *sk,
 	bpf_compute_and_save_data_end(skb, &saved_data_end);
 
 	if (atype == CGROUP_INET_EGRESS) {
-		ret = BPF_PROG_CGROUP_INET_EGRESS_RUN_ARRAY(
-			cgrp->bpf.effective[atype], skb, __bpf_prog_run_save_cb);
+		u32 flags = 0;
+		bool cn;
+
+		ret = bpf_prog_run_array_cg_flags(
+			&cgrp->bpf, atype,
+			skb, __bpf_prog_run_save_cb, 0, &flags);
+
+		/* Return values of CGROUP EGRESS BPF programs are:
+		 *   0: drop packet
+		 *   1: keep packet
+		 *   2: drop packet and cn
+		 *   3: keep packet and cn
+		 *
+		 * The returned value is then converted to one of the NET_XMIT
+		 * or an error code that is then interpreted as drop packet
+		 * (and no cn):
+		 *   0: NET_XMIT_SUCCESS  skb should be transmitted
+		 *   1: NET_XMIT_DROP     skb should be dropped and cn
+		 *   2: NET_XMIT_CN       skb should be transmitted and cn
+		 *   3: -err              skb should be dropped
+		 */
+
+		cn = flags & BPF_RET_SET_CN;
+		if (ret && !IS_ERR_VALUE((long)ret))
+			ret = -EFAULT;
+		if (!ret)
+			ret = (cn ? NET_XMIT_CN : NET_XMIT_SUCCESS);
+		else
+			ret = (cn ? NET_XMIT_DROP : ret);
 	} else {
-		ret = BPF_PROG_RUN_ARRAY_CG(cgrp->bpf.effective[atype], skb,
-					    __bpf_prog_run_save_cb, 0);
+		ret = bpf_prog_run_array_cg(&cgrp->bpf, atype,
+					    skb, __bpf_prog_run_save_cb, 0);
 		if (ret && !IS_ERR_VALUE((long)ret))
 			ret = -EFAULT;
 	}
@@ -1109,8 +1202,7 @@ int __cgroup_bpf_run_filter_sk(struct sock *sk,
 {
 	struct cgroup *cgrp = sock_cgroup_ptr(&sk->sk_cgrp_data);
 
-	return BPF_PROG_RUN_ARRAY_CG(cgrp->bpf.effective[atype], sk,
-				     bpf_prog_run, 0);
+	return bpf_prog_run_array_cg(&cgrp->bpf, atype, sk, bpf_prog_run, 0);
 }
 EXPORT_SYMBOL(__cgroup_bpf_run_filter_sk);
 
@@ -1155,8 +1247,8 @@ int __cgroup_bpf_run_filter_sock_addr(struct sock *sk,
 	}
 
 	cgrp = sock_cgroup_ptr(&sk->sk_cgrp_data);
-	return BPF_PROG_RUN_ARRAY_CG_FLAGS(cgrp->bpf.effective[atype], &ctx,
-					   bpf_prog_run, 0, flags);
+	return bpf_prog_run_array_cg_flags(&cgrp->bpf, atype,
+					   &ctx, bpf_prog_run, 0, flags);
 }
 EXPORT_SYMBOL(__cgroup_bpf_run_filter_sock_addr);
 
@@ -1182,8 +1274,8 @@ int __cgroup_bpf_run_filter_sock_ops(struct sock *sk,
 {
 	struct cgroup *cgrp = sock_cgroup_ptr(&sk->sk_cgrp_data);
 
-	return BPF_PROG_RUN_ARRAY_CG(cgrp->bpf.effective[atype], sock_ops,
-				     bpf_prog_run, 0);
+	return bpf_prog_run_array_cg(&cgrp->bpf, atype, sock_ops, bpf_prog_run,
+				     0);
 }
 EXPORT_SYMBOL(__cgroup_bpf_run_filter_sock_ops);
 
@@ -1200,8 +1292,7 @@ int __cgroup_bpf_check_dev_permission(short dev_type, u32 major, u32 minor,
 
 	rcu_read_lock();
 	cgrp = task_dfl_cgroup(current);
-	ret = BPF_PROG_RUN_ARRAY_CG(cgrp->bpf.effective[atype], &ctx,
-				    bpf_prog_run, 0);
+	ret = bpf_prog_run_array_cg(&cgrp->bpf, atype, &ctx, bpf_prog_run, 0);
 	rcu_read_unlock();
 
 	return ret;
@@ -1366,8 +1457,7 @@ int __cgroup_bpf_run_filter_sysctl(struct ctl_table_header *head,
 
 	rcu_read_lock();
 	cgrp = task_dfl_cgroup(current);
-	ret = BPF_PROG_RUN_ARRAY_CG(cgrp->bpf.effective[atype], &ctx,
-				    bpf_prog_run, 0);
+	ret = bpf_prog_run_array_cg(&cgrp->bpf, atype, &ctx, bpf_prog_run, 0);
 	rcu_read_unlock();
 
 	kfree(ctx.cur_val);
@@ -1459,7 +1549,7 @@ int __cgroup_bpf_run_filter_setsockopt(struct sock *sk, int *level,
 	}
 
 	lock_sock(sk);
-	ret = BPF_PROG_RUN_ARRAY_CG(cgrp->bpf.effective[CGROUP_SETSOCKOPT],
+	ret = bpf_prog_run_array_cg(&cgrp->bpf, CGROUP_SETSOCKOPT,
 				    &ctx, bpf_prog_run, 0);
 	release_sock(sk);
 
@@ -1559,7 +1649,7 @@ int __cgroup_bpf_run_filter_getsockopt(struct sock *sk, int level,
 	}
 
 	lock_sock(sk);
-	ret = BPF_PROG_RUN_ARRAY_CG(cgrp->bpf.effective[CGROUP_GETSOCKOPT],
+	ret = bpf_prog_run_array_cg(&cgrp->bpf, CGROUP_GETSOCKOPT,
 				    &ctx, bpf_prog_run, retval);
 	release_sock(sk);
 
@@ -1608,7 +1698,7 @@ int __cgroup_bpf_run_filter_getsockopt_kern(struct sock *sk, int level,
 	 * be called if that data shouldn't be "exported".
 	 */
 
-	ret = BPF_PROG_RUN_ARRAY_CG(cgrp->bpf.effective[CGROUP_GETSOCKOPT],
+	ret = bpf_prog_run_array_cg(&cgrp->bpf, CGROUP_GETSOCKOPT,
 				    &ctx, bpf_prog_run, retval);
 	if (ret < 0)
 		return ret;