On Thu, Apr 25, 2024 at 6:59 AM Benjamin Tissoires <bentiss@xxxxxxxxxx> 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>
> ---
> kernel/bpf/hashtab.c | 16 +++++-----------
> 1 file changed, 5 insertions(+), 11 deletions(-)
>
> diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
> index 0179183c543a..20162ae741e9 100644
> --- a/kernel/bpf/hashtab.c
> +++ b/kernel/bpf/hashtab.c
> @@ -1515,7 +1515,7 @@ 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_or_wq(struct bpf_htab *htab)
> {
> int i;
>
> @@ -1527,10 +1527,10 @@ 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));
> }
> @@ -1544,18 +1544,12 @@ 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 (btf_record_has_field(htab->map.record, BPF_TIMER | BPF_WORKQUEUE)) {
> if (!htab_is_prealloc(htab))
> - htab_free_malloced_timers_or_wq(htab, true);
> + htab_free_malloced_timers_or_wq(htab);
> else
> htab_free_prealloced_timers(htab);
> }
> - if (btf_record_has_field(htab->map.record, BPF_WORKQUEUE)) {
> - if (!htab_is_prealloc(htab))
> - htab_free_malloced_timers_or_wq(htab, false);
> - else
> - htab_free_prealloced_wq(htab);
This looks wrong.
htab_free_prealloced_wq() is now unused as compiler says:
../kernel/bpf/hashtab.c:243:13: warning: ‘htab_free_prealloced_wq’
defined but not used [-Wunused-function]
243 | static void htab_free_prealloced_wq(struct bpf_htab *htab)
| ^~~~~~~~~~~~~~~~~~~~~~~
and prealloced maps with wq leak wq-s.
pw-bot: cr
