Commit dc1508a5 authored Aug 09, 2018 by Yonghong Song Committed by Daniel Borkmann Aug 10, 2018

bpf: fix bpffs non-array map seq_show issue



In function map_seq_next() of kernel/bpf/inode.c,
the first key will be the "0" regardless of the map type.
This works for array. But for hash type, if it happens
key "0" is in the map, the bpffs map show will miss
some items if the key "0" is not the first element of
the first bucket.

This patch fixed the issue by guaranteeing to get
the first element, if the seq_show is just started,
by passing NULL pointer key to map_get_next_key() callback.
This way, no missing elements will occur for
bpffs hash table show even if key "0" is in the map.

Fixes: a26ca7c9 ("bpf: btf: Add pretty print support to the basic arraymap")
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

parent 60afdf06

kernel/bpf/inode.c

+5 −3

Original line number	Diff line number	Diff line
		@@ -196,19 +196,21 @@ static void map_seq_next(struct seq_file m, void v, loff_t pos)
		{
		struct bpf_map *map = seq_file_to_map(m);
		void *key = map_iter(m)->key;
		void *prev_key;

		if (map_iter(m)->done)
		return NULL;

		if (unlikely(v == SEQ_START_TOKEN))
		goto done;
		prev_key = NULL;
		else
		prev_key = key;

		if (map->ops->map_get_next_key(map, key, key)) {
		if (map->ops->map_get_next_key(map, prev_key, key)) {
		map_iter(m)->done = true;
		return NULL;
		}

		done:
		++(*pos);
		return key;
		}

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