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

stable inclusion
from stable-v5.10.138
commit d7ad7e65aa2fb5608b3b499aeaf1697f2e2e0cfd
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I60QFD

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d7ad7e65aa2fb5608b3b499aeaf1697f2e2e0cfd

--------------------------------

commit 3c5f6e69 upstream.

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: 5ce6e77c ("bpf: Implement bpf iterator for sock local storage map")
Signed-off-by: NHou Tao <houtao1@huawei.com>
Acked-by: NYonghong Song <yhs@fb.com>
Acked-by: NMartin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/r/20220810080538.1845898-4-houtao@huaweicloud.comSigned-off-by: NAlexei Starovoitov <ast@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
Reviewed-by: NWei Li <liwei391@huawei.com>

net/core/bpf_sk_storage.c

@@ -794,10 +794,18 @@ 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)
@@ -843,7 +851,7 @@ 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),
 };