bpf: Acquire map uref in .init_seq_private for sock local storage map iterator

bpf_iter_attach_map() acquires a map uref, and the uref may be released
before or in the middle of iterating map elements. For example, the uref
could be released in bpf_iter_detach_map() as part of
bpf_link_release(), or could be released in bpf_map_put_with_uref() as
part of bpf_map_release().

So acquiring an extra map uref in bpf_iter_init_sk_storage_map() and
releasing it in bpf_iter_fini_sk_storage_map().

Fixes: d350731594f0 ("bpf: Implement bpf iterator for sock local storage map")
Signed-off-by: Hou Tao <houtao1@huawei.com>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/r/20220810080538.1845898-4-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/net/core/bpf_sk_storage.c b/net/core/bpf_sk_storage.c
index a25ec93729b97ef6f53a2d81dc0f61ebc420a439..83b89ba824d71f85a429bb29a354d8fd35fa8c20 100644 (file)
--- a/net/core/bpf_sk_storage.c
+++ b/net/core/bpf_sk_storage.c
@@ -875,10 +875,18 @@ static int bpf_iter_init_sk_storage_map(void *priv_data,
 {
        struct bpf_iter_seq_sk_storage_map_info *seq_info = priv_data;
 
+       bpf_map_inc_with_uref(aux->map);
        seq_info->map = aux->map;
        return 0;
 }
 
+static void bpf_iter_fini_sk_storage_map(void *priv_data)
+{
+       struct bpf_iter_seq_sk_storage_map_info *seq_info = priv_data;
+
+       bpf_map_put_with_uref(seq_info->map);
+}
+
 static int bpf_iter_attach_map(struct bpf_prog *prog,
                               union bpf_iter_link_info *linfo,
                               struct bpf_iter_aux_info *aux)
@@ -924,7 +932,7 @@ static const struct seq_operations bpf_sk_storage_map_seq_ops = {
 static const struct bpf_iter_seq_info iter_seq_info = {
        .seq_ops                = &bpf_sk_storage_map_seq_ops,
        .init_seq_private       = bpf_iter_init_sk_storage_map,
-       .fini_seq_private       = NULL,
+       .fini_seq_private       = bpf_iter_fini_sk_storage_map,
        .seq_priv_size          = sizeof(struct bpf_iter_seq_sk_storage_map_info),
 };