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Wed, 29 Jul 2026 13:29:56 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Wed, 29 Jul 2026 16:29:53 -0400 Message-Id: From: "Emil Tsalapatis" To: "Michal Luczaj" , "Eric Dumazet" , "Kuniyuki Iwashima" , "Paolo Abeni" , "Willem de Bruijn" , "John Fastabend" , "Jakub Sitnicki" , "Jiayuan Chen" , "David S. Miller" , "Jakub Kicinski" , "Simon Horman" , "Daniel Borkmann" , "Stanislav Fomichev" , "Martin KaFai Lau" , "Alexei Starovoitov" , "Andrii Nakryiko" , "Eduard Zingerman" , "Kumar Kartikeya Dwivedi" , "Song Liu" , "Yonghong Song" , "Jiri Olsa" , "Emil Tsalapatis" , "Joe Stringer" Cc: , , Subject: Re: [PATCH bpf 1/3] bpf, sockmap: Use sock_hold() instead of refcount_inc_not_zero() in lookup X-Mailer: aerc 0.21.0-0-g5549850facc2 References: <20260723-sockmap-lookup-tcp-leak-v1-0-1bbdc58ce514@rbox.co> <20260723-sockmap-lookup-tcp-leak-v1-1-1bbdc58ce514@rbox.co> In-Reply-To: <20260723-sockmap-lookup-tcp-leak-v1-1-1bbdc58ce514@rbox.co> On Thu Jul 23, 2026 at 7:33 AM EDT, 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 >=3D 1: > refcount_inc_not_zero() can never fail here. Use sock_hold() instead. > > Signed-off-by: Michal Luczaj Reviewed-by: Emil Tsalapatis > --- > 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, voi= d *key) > sk =3D __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; > } > =20 > @@ -1218,8 +1218,8 @@ static void *sock_hash_lookup(struct bpf_map *map, = void *key) > sk =3D __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; > } > =20