On Apr 30 2024, Benjamin Tissoires wrote:
> If someone stores both a timer and a workqueue in a hash map, on free, we
> would walk it twice.
> Add a check in htab_free_malloced_timers_or_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@xxxxxxxxxx>
>
> ---
>
> changes in v2:
> - fix wq being not freed (and static call not used)
> ---
> kernel/bpf/hashtab.c | 49 +++++++++++++------------------------------------
> 1 file changed, 13 insertions(+), 36 deletions(-)
>
> diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
> index 0179183c543a..5eefadfc8ea9 100644
> --- a/kernel/bpf/hashtab.c
> +++ b/kernel/bpf/hashtab.c
> @@ -221,32 +221,11 @@ static bool htab_has_extra_elems(struct bpf_htab *htab)
> return !htab_is_percpu(htab) && !htab_is_lru(htab);
> }
>
> -static void htab_free_prealloced_timers(struct bpf_htab *htab)
> +static void htab_free_prealloced_timers_and_wq(struct bpf_htab *htab)
> {
> u32 num_entries = htab->map.max_entries;
> int i;
>
> - if (!btf_record_has_field(htab->map.record, BPF_TIMER))
> - return;
> - if (htab_has_extra_elems(htab))
> - num_entries += num_possible_cpus();
> -
> - for (i = 0; i < num_entries; i++) {
> - struct htab_elem *elem;
> -
> - elem = get_htab_elem(htab, i);
> - bpf_obj_free_timer(htab->map.record, elem->key + round_up(htab->map.key_size, 8));
> - cond_resched();
> - }
> -}
> -
> -static void htab_free_prealloced_wq(struct bpf_htab *htab)
> -{
> - u32 num_entries = htab->map.max_entries;
> - int i;
> -
> - if (!btf_record_has_field(htab->map.record, BPF_WORKQUEUE))
> - return;
> if (htab_has_extra_elems(htab))
> num_entries += num_possible_cpus();
>
> @@ -254,8 +233,12 @@ static void htab_free_prealloced_wq(struct bpf_htab *htab)
> struct htab_elem *elem;
>
> elem = get_htab_elem(htab, i);
> - bpf_obj_free_workqueue(htab->map.record,
> - elem->key + round_up(htab->map.key_size, 8));
> + if (btf_record_has_field(htab->map.record, BPF_TIMER))
> + bpf_obj_free_timer(htab->map.record,
> + elem->key + round_up(htab->map.key_size, 8));
> + else
Sorry, this else above is wrong, it should be a check on BPF_WORKQUEUE
instead.
v3 is n its way (with the proper bpf-next suffix this time).
Cheers,
Benjamin
> + bpf_obj_free_workqueue(htab->map.record,
> + elem->key + round_up(htab->map.key_size, 8));
> cond_resched();
> }
> }
> @@ -1515,7 +1498,7 @@ static void delete_all_elements(struct bpf_htab *htab)
> migrate_enable();
> }
>
> -static void htab_free_malloced_timers_or_wq(struct bpf_htab *htab, bool is_timer)
> +static void htab_free_malloced_timers_and_wq(struct bpf_htab *htab)
> {
> int i;
>
> @@ -1527,10 +1510,10 @@ static void htab_free_malloced_timers_or_wq(struct bpf_htab *htab, bool is_timer
>
> hlist_nulls_for_each_entry(l, n, head, hash_node) {
> /* We only free timer on uref dropping to zero */
> - if (is_timer)
> + if (btf_record_has_field(htab->map.record, BPF_TIMER))
> bpf_obj_free_timer(htab->map.record,
> l->key + round_up(htab->map.key_size, 8));
> - else
> + if (btf_record_has_field(htab->map.record, BPF_WORKQUEUE))
> bpf_obj_free_workqueue(htab->map.record,
> l->key + round_up(htab->map.key_size, 8));
> }
> @@ -1544,17 +1527,11 @@ static void htab_map_free_timers_and_wq(struct bpf_map *map)
> struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
>
> /* We only free timer and workqueue on uref dropping to zero */
> - if (btf_record_has_field(htab->map.record, BPF_TIMER)) {
> - if (!htab_is_prealloc(htab))
> - htab_free_malloced_timers_or_wq(htab, true);
> - else
> - htab_free_prealloced_timers(htab);
> - }
> - if (btf_record_has_field(htab->map.record, BPF_WORKQUEUE)) {
> + if (btf_record_has_field(htab->map.record, BPF_TIMER | BPF_WORKQUEUE)) {
> if (!htab_is_prealloc(htab))
> - htab_free_malloced_timers_or_wq(htab, false);
> + htab_free_malloced_timers_and_wq(htab);
> else
> - htab_free_prealloced_wq(htab);
> + htab_free_prealloced_timers_and_wq(htab);
> }
> }
>
>
> --
> 2.44.0
>
