[PATCH 2/3] bpf: do not walk twice the hash map on free

[Benjamin Tissoires <bentiss@kernel.org>]

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@kernel.org>
---
 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);
-	}
 }
 
 /* Called when map->refcnt goes to zero, either from workqueue or from syscall */

-- 
2.44.0