From: John Fastabend <john.fastabend@gmail.com>
To: Michal Luczaj <mhal@rbox.co>
Cc: Eric Dumazet <edumazet@google.com>,
Kuniyuki Iwashima <kuniyu@google.com>,
Paolo Abeni <pabeni@redhat.com>,
Willem de Bruijn <willemb@google.com>,
Jakub Sitnicki <jakub@cloudflare.com>,
Jiayuan Chen <jiayuan.chen@linux.dev>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Simon Horman <horms@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Stanislav Fomichev <sdf@fomichev.me>,
Martin KaFai Lau <martin.lau@linux.dev>,
Alexei Starovoitov <ast@kernel.org>,
Andrii Nakryiko <andrii@kernel.org>,
Eduard Zingerman <eddyz87@gmail.com>,
Kumar Kartikeya Dwivedi <memxor@gmail.com>,
Song Liu <song@kernel.org>,
Yonghong Song <yonghong.song@linux.dev>,
Jiri Olsa <jolsa@kernel.org>,
Emil Tsalapatis <emil@etsalapatis.com>,
Joe Stringer <joe@wand.net.nz>,
netdev@vger.kernel.org, bpf@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH bpf 1/3] bpf, sockmap: Use sock_hold() instead of refcount_inc_not_zero() in lookup
Date: Fri, 24 Jul 2026 17:00:05 -0700 [thread overview]
Message-ID: <amP8aYwtxo5qJUEb@john-p8> (raw)
In-Reply-To: <20260723-sockmap-lookup-tcp-leak-v1-1-1bbdc58ce514@rbox.co>
On Thu, Jul 23, 2026 at 01:33:27PM +0200, Michal Luczaj wrote:
>psock's hold on the looked up socket isn't dropped until sk_psock_drop() ->
>queue_rcu_work() -> sk_psock_destroy() runs, which happens only after the
>entry is unlinked and an RCU grace period elapses. Since the lookup runs
>under RCU, a non-NULL result guarantees sk_refcnt >= 1:
>refcount_inc_not_zero() can never fail here. Use sock_hold() instead.
>
>Signed-off-by: Michal Luczaj <mhal@rbox.co>
>---
Should bpf-next right? this is an optimization not a fix?
> net/core/sock_map.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
>diff --git a/net/core/sock_map.c b/net/core/sock_map.c
>index 9efbd8ca7db8..ca49bc7f8687 100644
>--- a/net/core/sock_map.c
>+++ b/net/core/sock_map.c
>@@ -392,8 +392,8 @@ static void *sock_map_lookup(struct bpf_map *map, void *key)
> sk = __sock_map_lookup_elem(map, *(u32 *)key);
> if (!sk)
> return NULL;
>- if (sk_is_refcounted(sk) && !refcount_inc_not_zero(&sk->sk_refcnt))
>- return NULL;
>+ if (sk_is_refcounted(sk))
>+ sock_hold(sk);
> return sk;
> }
>
>@@ -1218,8 +1218,8 @@ static void *sock_hash_lookup(struct bpf_map *map, void *key)
> sk = __sock_hash_lookup_elem(map, key);
> if (!sk)
> return NULL;
>- if (sk_is_refcounted(sk) && !refcount_inc_not_zero(&sk->sk_refcnt))
>- return NULL;
>+ if (sk_is_refcounted(sk))
>+ sock_hold(sk);
> return sk;
> }
>
>
>--
>2.55.0
>
next prev parent reply other threads:[~2026-07-25 0:00 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-23 11:33 [PATCH bpf 0/3] bpf: Fix socket leaks around connect(AF_UNSPEC)+listen() Michal Luczaj
2026-07-23 11:33 ` [PATCH bpf 1/3] bpf, sockmap: Use sock_hold() instead of refcount_inc_not_zero() in lookup Michal Luczaj
2026-07-25 0:00 ` John Fastabend [this message]
2026-07-23 11:33 ` [PATCH bpf 2/3] bpf: Extract shared reqsk-to-listener upgrade Michal Luczaj
2026-07-23 11:33 ` [PATCH bpf 3/3] bpf: Unconditionally take socket references in lookup helpers Michal Luczaj
2026-07-23 15:25 ` bot+bpf-ci
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