[PATCH 5.15 045/244] bpf: Acquire map uref in .init_seq_private for hash map iterator

Greg Kroah-Hartman
2022-08-23T09:48:34Z

From: Hou Tao <houtao1@huawei.com>

commit ef1e93d2eeb58a1f08c37b22a2314b94bc045f15 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_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>
Link: https://lore.kernel.org/r/20220810080538.1845898-3-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
kernel/bpf/hashtab.c | 2 ++
1 file changed, 2 insertions(+)

--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -2019,6 +2019,7 @@ static int bpf_iter_init_hash_map(void *
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;
@@ -2028,6 +2029,7 @@ static void bpf_iter_fini_hash_map(void
{
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);
}