4.18-stable review patch. If anyone has any objections, please let me know.
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From: Yonghong Song yhs@fb.com
[ Upstream commit dc1508a579e682a1e5f1ed0753390e0aa7c23a97 ]
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: a26ca7c982cb5 ("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 Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/bpf/inode.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)
--- a/kernel/bpf/inode.c +++ b/kernel/bpf/inode.c @@ -196,19 +196,21 @@ static void *map_seq_next(struct seq_fil { 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; }