Commit f76fa6b3 authored Aug 10, 2022 by Hou Tao Committed by Alexei Starovoitov Aug 10, 2022

bpf: Acquire map uref in .init_seq_private for array 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().

Alternative fix is acquiring an extra bpf_link reference just like
a pinned map iterator does, but it introduces unnecessary dependency
on bpf_link instead of bpf_map.

So choose another fix: acquiring an extra map uref in .init_seq_private
for array map iterator.

Fixes: d3cc2ab5 ("bpf: Implement bpf iterator for array maps")
Signed-off-by: Hou Tao <houtao1@huawei.com>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20220810080538.1845898-2-houtao@huaweicloud.com


Signed-off-by: Alexei Starovoitov <ast@kernel.org>

parent 86f44fce

kernel/bpf/arraymap.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -649,6 +649,11 @@ static int bpf_iter_init_array_map(void *priv_data,
		seq_info->percpu_value_buf = value_buf;
		}

		/* bpf_iter_attach_map() acquires a map uref, and the uref may be
		* released before or in the middle of iterating map elements, so
		* acquire an extra map uref for iterator.
		*/
		bpf_map_inc_with_uref(map);
		seq_info->map = map;
		return 0;
		}
		@@ -657,6 +662,7 @@ static void bpf_iter_fini_array_map(void *priv_data)
		{
		struct bpf_iter_seq_array_map_info *seq_info = priv_data;

		bpf_map_put_with_uref(seq_info->map);
		kfree(seq_info->percpu_value_buf);
		}