From f76fa6b338055054f80c72b29c97fb95c1becadc Mon Sep 17 00:00:00 2001 From: Hou Tao Date: Wed, 10 Aug 2022 16:05:30 +0800 Subject: [PATCH] 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: d3cc2ab546ad ("bpf: Implement bpf iterator for array maps") Signed-off-by: Hou Tao Acked-by: Yonghong Song Link: https://lore.kernel.org/r/20220810080538.1845898-2-houtao@huaweicloud.com Signed-off-by: Alexei Starovoitov --- kernel/bpf/arraymap.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c index d3e734b..6245274 100644 --- a/kernel/bpf/arraymap.c +++ b/kernel/bpf/arraymap.c @@ -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); } -- 2.7.4