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

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Date: Tue, 30 Apr 2024 12:43:24 +0200
From: Benjamin Tissoires <bentiss@...nel.org>
To: Alexei Starovoitov <ast@...nel.org>, 
 Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>, 
 Martin KaFai Lau <martin.lau@...ux.dev>, 
 Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
 Yonghong Song <yonghong.song@...ux.dev>, 
 John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>, 
 Stanislav Fomichev <sdf@...gle.com>, Hao Luo <haoluo@...gle.com>, 
 Jiri Olsa <jolsa@...nel.org>, Mykola Lysenko <mykolal@...com>, 
 Shuah Khan <shuah@...nel.org>
Cc: bpf@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-kselftest@...r.kernel.org, Benjamin Tissoires <bentiss@...nel.org>
Subject: [PATCH bpf-next v3 1/3] bpf: do not walk twice the map on free

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@...nel.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