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bpf: Acquire map uref in .init_seq_private for array map iterator

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commit f76fa6b338 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().

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: d3cc2ab546 ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Hou Tao 2022-08-10 16:05:30 +08:00 committed by Greg Kroah-Hartman
parent 76ffd20424
commit 30d7198da8
1 changed files with 6 additions and 0 deletions
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6
kernel/bpf/arraymap.c
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@ -616,6 +616,11 @@ static int bpf_iter_init_array_map(void *priv_data,
seq_info->percpu_value_buf = value_buf; 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; seq_info->map = map;
return 0; return 0;
} }
@ -624,6 +629,7 @@ static void bpf_iter_fini_array_map(void *priv_data)
{ {
struct bpf_iter_seq_array_map_info *seq_info = 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); kfree(seq_info->percpu_value_buf);
} }