bpf: support BPF_PROG_QUERY for progs attached to sockmap

Right now there is no way to query whether BPF programs are
attached to a sockmap or not.

we can use the standard interface in libbpf to query, such as:
bpf_prog_query(mapFd, BPF_SK_SKB_STREAM_PARSER, 0, NULL, ...);
the mapFd is the fd of sockmap.

Signed-off-by: Di Zhu <zhudi2@huawei.com>
Acked-by: Yonghong Song <yhs@fb.com>
Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
Link: https://lore.kernel.org/r/20220119014005.1209-1-zhudi2@huawei.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index dce54eb..80e3387 100644 (file)
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2069,6 +2069,9 @@ int bpf_prog_test_run_syscall(struct bpf_prog *prog,
 int sock_map_get_from_fd(const union bpf_attr *attr, struct bpf_prog *prog);
 int sock_map_prog_detach(const union bpf_attr *attr, enum bpf_prog_type ptype);
 int sock_map_update_elem_sys(struct bpf_map *map, void *key, void *value, u64 flags);
+int sock_map_bpf_prog_query(const union bpf_attr *attr,
+                           union bpf_attr __user *uattr);
+
 void sock_map_unhash(struct sock *sk);
 void sock_map_close(struct sock *sk, long timeout);
 #else
@@ -2122,6 +2125,12 @@ static inline int sock_map_update_elem_sys(struct bpf_map *map, void *key, void
 {
        return -EOPNOTSUPP;
 }
+
+static inline int sock_map_bpf_prog_query(const union bpf_attr *attr,
+                                         union bpf_attr __user *uattr)
+{
+       return -EINVAL;
+}
 #endif /* CONFIG_BPF_SYSCALL */
 #endif /* CONFIG_NET && CONFIG_BPF_SYSCALL */
 

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index fa4505f..9e0631f 100644 (file)
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -3318,6 +3318,11 @@ static int bpf_prog_query(const union bpf_attr *attr,
        case BPF_FLOW_DISSECTOR:
        case BPF_SK_LOOKUP:
                return netns_bpf_prog_query(attr, uattr);
+       case BPF_SK_SKB_STREAM_PARSER:
+       case BPF_SK_SKB_STREAM_VERDICT:
+       case BPF_SK_MSG_VERDICT:
+       case BPF_SK_SKB_VERDICT:
+               return sock_map_bpf_prog_query(attr, uattr);
        default:
                return -EINVAL;
        }

diff --git a/net/core/sock_map.c b/net/core/sock_map.c
index 1827669..2d213c4 100644 (file)
--- a/net/core/sock_map.c
+++ b/net/core/sock_map.c
@@ -1416,38 +1416,50 @@ static struct sk_psock_progs *sock_map_progs(struct bpf_map *map)
        return NULL;
 }
 
-static int sock_map_prog_update(struct bpf_map *map, struct bpf_prog *prog,
-                               struct bpf_prog *old, u32 which)
+static int sock_map_prog_lookup(struct bpf_map *map, struct bpf_prog ***pprog,
+                               u32 which)
 {
        struct sk_psock_progs *progs = sock_map_progs(map);
-       struct bpf_prog **pprog;
 
        if (!progs)
                return -EOPNOTSUPP;
 
        switch (which) {
        case BPF_SK_MSG_VERDICT:
-               pprog = &progs->msg_parser;
+               *pprog = &progs->msg_parser;
                break;
 #if IS_ENABLED(CONFIG_BPF_STREAM_PARSER)
        case BPF_SK_SKB_STREAM_PARSER:
-               pprog = &progs->stream_parser;
+               *pprog = &progs->stream_parser;
                break;
 #endif
        case BPF_SK_SKB_STREAM_VERDICT:
                if (progs->skb_verdict)
                        return -EBUSY;
-               pprog = &progs->stream_verdict;
+               *pprog = &progs->stream_verdict;
                break;
        case BPF_SK_SKB_VERDICT:
                if (progs->stream_verdict)
                        return -EBUSY;
-               pprog = &progs->skb_verdict;
+               *pprog = &progs->skb_verdict;
                break;
        default:
                return -EOPNOTSUPP;
        }
 
+       return 0;
+}
+
+static int sock_map_prog_update(struct bpf_map *map, struct bpf_prog *prog,
+                               struct bpf_prog *old, u32 which)
+{
+       struct bpf_prog **pprog;
+       int ret;
+
+       ret = sock_map_prog_lookup(map, &pprog, which);
+       if (ret)
+               return ret;
+
        if (old)
                return psock_replace_prog(pprog, prog, old);
 
@@ -1455,6 +1467,57 @@ static int sock_map_prog_update(struct bpf_map *map, struct bpf_prog *prog,
        return 0;
 }
 
+int sock_map_bpf_prog_query(const union bpf_attr *attr,
+                           union bpf_attr __user *uattr)
+{
+       __u32 __user *prog_ids = u64_to_user_ptr(attr->query.prog_ids);
+       u32 prog_cnt = 0, flags = 0, ufd = attr->target_fd;
+       struct bpf_prog **pprog;
+       struct bpf_prog *prog;
+       struct bpf_map *map;
+       struct fd f;
+       u32 id = 0;
+       int ret;
+
+       if (attr->query.query_flags)
+               return -EINVAL;
+
+       f = fdget(ufd);
+       map = __bpf_map_get(f);
+       if (IS_ERR(map))
+               return PTR_ERR(map);
+
+       rcu_read_lock();
+
+       ret = sock_map_prog_lookup(map, &pprog, attr->query.attach_type);
+       if (ret)
+               goto end;
+
+       prog = *pprog;
+       prog_cnt = !prog ? 0 : 1;
+
+       if (!attr->query.prog_cnt || !prog_ids || !prog_cnt)
+               goto end;
+
+       /* we do not hold the refcnt, the bpf prog may be released
+        * asynchronously and the id would be set to 0.
+        */
+       id = data_race(prog->aux->id);
+       if (id == 0)
+               prog_cnt = 0;
+
+end:
+       rcu_read_unlock();
+
+       if (copy_to_user(&uattr->query.attach_flags, &flags, sizeof(flags)) ||
+           (id != 0 && copy_to_user(prog_ids, &id, sizeof(u32))) ||
+           copy_to_user(&uattr->query.prog_cnt, &prog_cnt, sizeof(prog_cnt)))
+               ret = -EFAULT;
+
+       fdput(f);
+       return ret;
+}
+
 static void sock_map_unlink(struct sock *sk, struct sk_psock_link *link)
 {
        switch (link->map->map_type) {