linux-kernel - [PATCH bpf-next] bpf: hashtab - allow BPF_MAP_LOOKUP{,_AND_DELETE}

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Message-ID: <20250813073955.1775315-1-maze@google.com>
Date: Wed, 13 Aug 2025 00:39:55 -0700
From: "Maciej Żenczykowski" <maze@...gle.com>
To: "Maciej Żenczykowski" <zenczykowski@...il.com>, Alexei Starovoitov <ast@...nel.org>, 
	Daniel Borkmann <daniel@...earbox.net>
Cc: Linux Network Development Mailing List <netdev@...r.kernel.org>, "David S . Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, BPF Mailing List <bpf@...r.kernel.org>, 
	"Maciej Żenczykowski" <maze@...gle.com>, Stanislav Fomichev <sdf@...ichev.me>
Subject: [PATCH bpf-next] bpf: hashtab - allow BPF_MAP_LOOKUP{,_AND_DELETE}_BATCH
 with NULL keys/values.

BPF_MAP_LOOKUP_AND_DELETE_BATCH keys & values == NULL
seems like a nice way to simply quickly clear a map.

BPF_MAP_LOOKUP keys/values == NULL might be useful if we just want
the values/keys and don't want to bother copying the keys/values...

BPF_MAP_LOOKUP keys & values == NULL might be useful to count
the number of populated entries.

Cc: Alexei Starovoitov <ast@...nel.org>
Cc: Daniel Borkmann <daniel@...earbox.net>
Cc: Stanislav Fomichev <sdf@...ichev.me>
Signed-off-by: Maciej Żenczykowski <maze@...gle.com>
---
 kernel/bpf/hashtab.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index 5001131598e5..8fbdd000d9e0 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -1873,9 +1873,9 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map,
 
 	rcu_read_unlock();
 	bpf_enable_instrumentation();
-	if (bucket_cnt && (copy_to_user(ukeys + total * key_size, keys,
+	if (bucket_cnt && (ukeys && copy_to_user(ukeys + total * key_size, keys,
 	    key_size * bucket_cnt) ||
-	    copy_to_user(uvalues + total * value_size, values,
+	    uvalues && copy_to_user(uvalues + total * value_size, values,
 	    value_size * bucket_cnt))) {
 		ret = -EFAULT;
 		goto after_loop;
-- 
2.51.0.rc1.163.g2494970778-goog