net: sched: rcu'ify cls_bpf

This patch makes the cls_bpf classifier RCU safe. The tcf_lock
was being used to protect a list of cls_bpf_prog now this list
is RCU safe and updates occur with rcu_replace.

Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 47 insertions, 47 deletions

diff --git a/net/sched/cls_bpf.c b/net/sched/cls_bpf.c
index 0e30d58149da..6a7386e6e5a8 100644
--- a/net/sched/cls_bpf.c
+++ b/net/sched/cls_bpf.c
@@ -27,6 +27,7 @@ MODULE_DESCRIPTION("TC BPF based classifier");
 struct cls_bpf_head {
         struct list_head plist;
         u32 hgen;
+        struct rcu_head rcu;
 };
 
 struct cls_bpf_prog {
@@ -37,6 +38,8 @@ struct cls_bpf_prog {
         struct list_head link;
         u32 handle;
         u16 bpf_len;
+        struct tcf_proto *tp;
+        struct rcu_head rcu;
 };
 
 static const struct nla_policy bpf_policy[TCA_BPF_MAX + 1] = {
@@ -49,11 +52,11 @@ static const struct nla_policy bpf_policy[TCA_BPF_MAX + 1] = {
 static int cls_bpf_classify(struct sk_buff *skb, const struct tcf_proto *tp,
                             struct tcf_result *res)
 {
-        struct cls_bpf_head *head = tp->root;
+        struct cls_bpf_head *head = rcu_dereference(tp->root);
         struct cls_bpf_prog *prog;
         int ret;
 
-        list_for_each_entry(prog, &head->plist, link) {
+        list_for_each_entry_rcu(prog, &head->plist, link) {
                 int filter_res = BPF_PROG_RUN(prog->filter, skb);
 
                 if (filter_res == 0)
@@ -81,8 +84,8 @@ static int cls_bpf_init(struct tcf_proto *tp)
         if (head == NULL)
                 return -ENOBUFS;
 
-        INIT_LIST_HEAD(&head->plist);
-        tp->root = head;
+        INIT_LIST_HEAD_RCU(&head->plist);
+        rcu_assign_pointer(tp->root, head);
 
         return 0;
 }
@@ -98,18 +101,22 @@ static void cls_bpf_delete_prog(struct tcf_proto *tp, struct cls_bpf_prog *prog)
         kfree(prog);
 }
 
+static void __cls_bpf_delete_prog(struct rcu_head *rcu)
+{
+        struct cls_bpf_prog *prog = container_of(rcu, struct cls_bpf_prog, rcu);
+
+        cls_bpf_delete_prog(prog->tp, prog);
+}
+
 static int cls_bpf_delete(struct tcf_proto *tp, unsigned long arg)
 {
-        struct cls_bpf_head *head = tp->root;
+        struct cls_bpf_head *head = rtnl_dereference(tp->root);
         struct cls_bpf_prog *prog, *todel = (struct cls_bpf_prog *) arg;
 
         list_for_each_entry(prog, &head->plist, link) {
                 if (prog == todel) {
-                        tcf_tree_lock(tp);
-                        list_del(&prog->link);
-                        tcf_tree_unlock(tp);
-
-                        cls_bpf_delete_prog(tp, prog);
+                        list_del_rcu(&prog->link);
+                        call_rcu(&prog->rcu, __cls_bpf_delete_prog);
                         return 0;
                 }
         }
@@ -119,27 +126,28 @@ static int cls_bpf_delete(struct tcf_proto *tp, unsigned long arg)
 
 static void cls_bpf_destroy(struct tcf_proto *tp)
 {
-        struct cls_bpf_head *head = tp->root;
+        struct cls_bpf_head *head = rtnl_dereference(tp->root);
         struct cls_bpf_prog *prog, *tmp;
 
         list_for_each_entry_safe(prog, tmp, &head->plist, link) {
-                list_del(&prog->link);
-                cls_bpf_delete_prog(tp, prog);
+                list_del_rcu(&prog->link);
+                call_rcu(&prog->rcu, __cls_bpf_delete_prog);
         }
 
-        kfree(head);
+        RCU_INIT_POINTER(tp->root, NULL);
+        kfree_rcu(head, rcu);
 }
 
 static unsigned long cls_bpf_get(struct tcf_proto *tp, u32 handle)
 {
-        struct cls_bpf_head *head = tp->root;
+        struct cls_bpf_head *head = rtnl_dereference(tp->root);
         struct cls_bpf_prog *prog;
         unsigned long ret = 0UL;
 
         if (head == NULL)
                 return 0UL;
 
-        list_for_each_entry(prog, &head->plist, link) {
+        list_for_each_entry_rcu(prog, &head->plist, link) {
                 if (prog->handle == handle) {
                         ret = (unsigned long) prog;
                         break;
@@ -158,10 +166,10 @@ static int cls_bpf_modify_existing(struct net *net, struct tcf_proto *tp,
                                    unsigned long base, struct nlattr **tb,
                                    struct nlattr *est, bool ovr)
 {
-        struct sock_filter *bpf_ops, *bpf_old;
+        struct sock_filter *bpf_ops;
         struct tcf_exts exts;
         struct sock_fprog_kern tmp;
-        struct bpf_prog *fp, *fp_old;
+        struct bpf_prog *fp;
         u16 bpf_size, bpf_len;
         u32 classid;
         int ret;
@@ -197,26 +205,15 @@ static int cls_bpf_modify_existing(struct net *net, struct tcf_proto *tp,
         if (ret)
                 goto errout_free;
 
-        tcf_tree_lock(tp);
-        fp_old = prog->filter;
-        bpf_old = prog->bpf_ops;
-
         prog->bpf_len = bpf_len;
         prog->bpf_ops = bpf_ops;
         prog->filter = fp;
         prog->res.classid = classid;
-        tcf_tree_unlock(tp);
 
         tcf_bind_filter(tp, &prog->res, base);
         tcf_exts_change(tp, &prog->exts, &exts);
 
-        if (fp_old)
-                bpf_prog_destroy(fp_old);
-        if (bpf_old)
-                kfree(bpf_old);
-
         return 0;
-
 errout_free:
         kfree(bpf_ops);
 errout:
@@ -244,9 +241,10 @@ static int cls_bpf_change(struct net *net, struct sk_buff *in_skb,
                           u32 handle, struct nlattr **tca,
                           unsigned long *arg, bool ovr)
 {
-        struct cls_bpf_head *head = tp->root;
-        struct cls_bpf_prog *prog = (struct cls_bpf_prog *) *arg;
+        struct cls_bpf_head *head = rtnl_dereference(tp->root);
+        struct cls_bpf_prog *oldprog = (struct cls_bpf_prog *) *arg;
         struct nlattr *tb[TCA_BPF_MAX + 1];
+        struct cls_bpf_prog *prog;
         int ret;
 
         if (tca[TCA_OPTIONS] == NULL)
@@ -256,18 +254,19 @@ static int cls_bpf_change(struct net *net, struct sk_buff *in_skb,
         if (ret < 0)
                 return ret;
 
-        if (prog != NULL) {
-                if (handle && prog->handle != handle)
-                        return -EINVAL;
-                return cls_bpf_modify_existing(net, tp, prog, base, tb,
-                                               tca[TCA_RATE], ovr);
-        }
-
         prog = kzalloc(sizeof(*prog), GFP_KERNEL);
-        if (prog == NULL)
+        if (!prog)
                 return -ENOBUFS;
 
         tcf_exts_init(&prog->exts, TCA_BPF_ACT, TCA_BPF_POLICE);
+
+        if (oldprog) {
+                if (handle && oldprog->handle != handle) {
+                        ret = -EINVAL;
+                        goto errout;
+                }
+        }
+
         if (handle == 0)
                 prog->handle = cls_bpf_grab_new_handle(tp, head);
         else
@@ -281,16 +280,17 @@ static int cls_bpf_change(struct net *net, struct sk_buff *in_skb,
         if (ret < 0)
                 goto errout;
 
-        tcf_tree_lock(tp);
-        list_add(&prog->link, &head->plist);
-        tcf_tree_unlock(tp);
+        if (oldprog) {
+                list_replace_rcu(&prog->link, &oldprog->link);
+                call_rcu(&oldprog->rcu, __cls_bpf_delete_prog);
+        } else {
+                list_add_rcu(&prog->link, &head->plist);
+        }
 
         *arg = (unsigned long) prog;
-
         return 0;
 errout:
-        if (*arg == 0UL && prog)
-                kfree(prog);
+        kfree(prog);
 
         return ret;
 }
@@ -339,10 +339,10 @@ nla_put_failure:
 
 static void cls_bpf_walk(struct tcf_proto *tp, struct tcf_walker *arg)
 {
-        struct cls_bpf_head *head = tp->root;
+        struct cls_bpf_head *head = rtnl_dereference(tp->root);
         struct cls_bpf_prog *prog;
 
-        list_for_each_entry(prog, &head->plist, link) {
+        list_for_each_entry_rcu(prog, &head->plist, link) {
                 if (arg->count < arg->skip)
                         goto skip;
                 if (arg->fn(tp, (unsigned long) prog, arg) < 0) {