[PATCH bpf-next v3 1/3] bpf: do not walk twice the map on free

Benjamin Tissoires
2024-04-30T10:43:37Z

If someone stores both a timer and a workqueue in a map, on free we
would walk it twice.
Add a check in array_map_free_timers_wq and free the timers
and workqueues if they are present.

Fixes: 246331e3f1ea ("bpf: allow struct bpf_wq to be embedded in arraymaps and hashmaps")
Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>

---

no changes in v3

no changes in v2
---
kernel/bpf/arraymap.c | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index 580d07b15471..feabc0193852 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -436,13 +436,14 @@ static void array_map_free_timers_wq(struct bpf_map *map)
/* We don't reset or free fields other than timer and workqueue
* on uref dropping to zero.
*/
- if (btf_record_has_field(map->record, BPF_TIMER))
- for (i = 0; i < array->map.max_entries; i++)
- bpf_obj_free_timer(map->record, array_map_elem_ptr(array, i));
-
- if (btf_record_has_field(map->record, BPF_WORKQUEUE))
- for (i = 0; i < array->map.max_entries; i++)
- bpf_obj_free_workqueue(map->record, array_map_elem_ptr(array, i));
+ if (btf_record_has_field(map->record, BPF_TIMER | BPF_WORKQUEUE)) {
+ for (i = 0; i < array->map.max_entries; i++) {
+ if (btf_record_has_field(map->record, BPF_TIMER))
+ bpf_obj_free_timer(map->record, array_map_elem_ptr(array, i));
+ if (btf_record_has_field(map->record, BPF_WORKQUEUE))
+ bpf_obj_free_workqueue(map->record, array_map_elem_ptr(array, i));
+ }
+ }
}

/* Called when map->refcnt goes to zero, either from workqueue or from syscall */

--
2.44.0