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[83.10.35.35]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-c260d03635csm243336466b.7.2026.09.05.09.38.31 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Sat, 05 Sep 2026 09:38:32 -0700 (PDT) From: Norbert Szetei Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3826.700.81.1.4\)) Subject: [PATCH net] net/sched: cls_u32: take a reference on the hash table in u32_change() Message-Id: <79DB27AC-0FC0-42B2-A795-A8B585B73CFB@doyensec.com> Date: Sat, 5 Sep 2026 18:38:20 +0200 Cc: Jamal Hadi Salim , Jiri Pirko , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Cong Wang , linux-kernel@vger.kernel.org To: netdev@vger.kernel.org X-Mailer: Apple Mail (2.3826.700.81.1.4) u32_change() keeps the target hash table in a local variable without taking a reference. u32_set_parms() may then drop rtnl to load an action module, and on a failed load returns without asking the caller to replay (-ENOENT). A concurrent RTM_DELTFILTER can free the table in that window, and u32_change() then removes the node id it reserved from the freed table. Take a reference on the table across u32_set_parms(). A racing u32_delete() then fails its refcount_dec_if_one() and returns -EBUSY instead of freeing it. Fixes: e7614370d6f0 ("net_sched: use idr to allocate u32 filter = handles") Assisted-by: Claude:claude-opus-5 Signed-off-by: Norbert Szetei --- Reproducer available on request. net/sched/cls_u32.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c index a3e65c8cf29e..0e9128f2f33e 100644 --- a/net/sched/cls_u32.c +++ b/net/sched/cls_u32.c @@ -1180,8 +1180,11 @@ static int u32_change(struct net *net, struct = sk_buff *in_skb, } #endif =20 + /* u32_set_parms() may drop rtnl; keep ht alive across it */ + refcount_inc(&ht->refcnt); err =3D u32_set_parms(net, tp, n, tb, tca[TCA_RATE], flags, n->flags, extack); + refcount_dec(&ht->refcnt); =20 u32_bind_filter(tp, n, base, tb); =20 --=20 2.55.0