[PATCH bpf 1/2] bpf: Check timer_off for map_in_map only when map value have timer

[Hengqi Chen <hengqi.chen@gmail.com>]

The timer_off value could be -EINVAL or -ENOENT when map value of
inner map is struct and contains no bpf_timer. The EINVAL case happens
when the map is created without BTF key/value info, map->timer_off
is set to -EINVAL in map_create(). The ENOENT case happens when
the map is created with BTF key/value info (e.g. from BPF skeleton),
map->timer_off is set to -ENOENT as what btf_find_timer() returns.
In bpf_map_meta_equal(), we expect timer_off to be equal even if
map value does not contains bpf_timer. This rejects map_in_map created
with BTF key/value info to be updated using inner map without BTF
key/value info in case inner map value is struct. This commit lifts
such restriction.

Fixes: 68134668c17f ("bpf: Add map side support for bpf timers.")
Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
---
 kernel/bpf/map_in_map.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/map_in_map.c b/kernel/bpf/map_in_map.c
index 135205d0d560..0840872de486 100644
--- a/kernel/bpf/map_in_map.c
+++ b/kernel/bpf/map_in_map.c
@@ -80,11 +80,18 @@ void bpf_map_meta_free(struct bpf_map *map_meta)
 bool bpf_map_meta_equal(const struct bpf_map *meta0,
 			const struct bpf_map *meta1)
 {
+	bool timer_off_equal;
+
+	if (!map_value_has_timer(meta0) && !map_value_has_timer(meta1))
+		timer_off_equal = true;
+	else
+		timer_off_equal = meta0->timer_off == meta1->timer_off;
+
 	/* No need to compare ops because it is covered by map_type */
 	return meta0->map_type == meta1->map_type &&
 		meta0->key_size == meta1->key_size &&
 		meta0->value_size == meta1->value_size &&
-		meta0->timer_off == meta1->timer_off &&
+		timer_off_equal &&
 		meta0->map_flags == meta1->map_flags &&
 		bpf_map_equal_kptr_off_tab(meta0, meta1);
 }
--
2.34.1