Merge branch 'bpf-sk-storage-clone'

Stanislav Fomichev says:

====================
Currently there is no way to propagate sk storage from the listener
socket to a newly accepted one. Consider the following use case:

        fd = socket();
        setsockopt(fd, SOL_IP, IP_TOS,...);
        /* ^^^ setsockopt BPF program triggers here and saves something
         * into sk storage of the listener.
         */
        listen(fd, ...);
        while (client = accept(fd)) {
                /* At this point all association between listener
                 * socket and newly accepted one is gone. New
                 * socket will not have any sk storage attached.
                 */
        }

Let's add new BPF_F_CLONE flag that can be specified when creating
a socket storage map. This new flag indicates that map contents
should be cloned when the socket is cloned.

v4:
* drop 'goto err' in bpf_sk_storage_clone (Yonghong Song)
* add comment about race with bpf_sk_storage_map_free to the
  bpf_sk_storage_clone side as well (Daniel Borkmann)

v3:
* make sure BPF_F_NO_PREALLOC is always present when creating
  a map (Martin KaFai Lau)
* don't call bpf_sk_storage_free explicitly, rely on
  sk_free_unlock_clone to do the cleanup (Martin KaFai Lau)

v2:
* remove spinlocks around selem_link_map/sk (Martin KaFai Lau)
* BPF_F_CLONE on a map, not selem (Martin KaFai Lau)
* hold a map while cloning (Martin KaFai Lau)
* use BTF maps in selftests (Yonghong Song)
* do proper cleanup selftests; don't call close(-1) (Yonghong Song)
* export bpf_map_inc_not_zero
====================

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

1 files changed, 13 insertions, 3 deletions

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 5d141f16f6fa..cf8052b016e7 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -683,8 +683,8 @@ struct bpf_map *bpf_map_get_with_uref(u32 ufd)
 }
 
 /* map_idr_lock should have been held */
-static struct bpf_map *bpf_map_inc_not_zero(struct bpf_map *map,
-					    bool uref)
+static struct bpf_map *__bpf_map_inc_not_zero(struct bpf_map *map,
+					      bool uref)
 {
 	int refold;
 
@@ -704,6 +704,16 @@ static struct bpf_map *bpf_map_inc_not_zero(struct bpf_map *map,
 	return map;
 }
 
+struct bpf_map *bpf_map_inc_not_zero(struct bpf_map *map, bool uref)
+{
+	spin_lock_bh(&map_idr_lock);
+	map = __bpf_map_inc_not_zero(map, uref);
+	spin_unlock_bh(&map_idr_lock);
+
+	return map;
+}
+EXPORT_SYMBOL_GPL(bpf_map_inc_not_zero);
+
 int __weak bpf_stackmap_copy(struct bpf_map *map, void *key, void *value)
 {
 	return -ENOTSUPP;
@@ -2177,7 +2187,7 @@ static int bpf_map_get_fd_by_id(const union bpf_attr *attr)
 	spin_lock_bh(&map_idr_lock);
 	map = idr_find(&map_idr, id);
 	if (map)
-		map = bpf_map_inc_not_zero(map, true);
+		map = __bpf_map_inc_not_zero(map, true);
 	else
 		map = ERR_PTR(-ENOENT);
 	spin_unlock_bh(&map_idr_lock);