[PATCH bpf v2 2/9] bpf: Acquire map uref in .init_seq_private for hash map iterator

[Hou Tao <houtao@huaweicloud.com>]

From: Hou Tao <houtao1@huawei.com>

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_hash_map() and
releasing it in bpf_iter_fini_hash_map().

Fixes: d6c4503cc296 ("bpf: Implement bpf iterator for hash maps")
Signed-off-by: Hou Tao <houtao1@huawei.com>
Acked-by: Yonghong Song <yhs@fb.com>
---
 kernel/bpf/hashtab.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index da7578426a46..da8c0177f773 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -2064,6 +2064,7 @@ static int bpf_iter_init_hash_map(void *priv_data,
 		seq_info->percpu_value_buf = value_buf;
 	}
 
+	bpf_map_inc_with_uref(map);
 	seq_info->map = map;
 	seq_info->htab = container_of(map, struct bpf_htab, map);
 	return 0;
@@ -2073,6 +2074,7 @@ static void bpf_iter_fini_hash_map(void *priv_data)
 {
 	struct bpf_iter_seq_hash_map_info *seq_info = priv_data;
 
+	bpf_map_put_with_uref(seq_info->map);
 	kfree(seq_info->percpu_value_buf);
 }
 
-- 
2.29.2