From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4AEC23CAE8D; Wed, 30 Sep 2026 19:08:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790795300; cv=none; b=kr+w5vHAHm35wMpKAmo/BklU8eBVdXYyAYBn/DKRzasoiYQBYznCF9QenVExkWhmivKLrW/oolzmN5S3GPe2MZk2pnLdXOJzyja8bm5iAcfEDF8gnzCT5TQ1GaXp792GgHf8NUDTF3B1gY+938GjQ66+khUzlZNqVSl7UaZFb7k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790795300; c=relaxed/simple; bh=1EnQRGLY0MTL79E28/S83vCJmdm/W0T9YczfYyzClnk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=LuCI3WEhdnlsF64OVwmPd+mCZV4oHBU62CmU4g4dr44S0l05EZuI2/qo5ZyAPktHMlpxN50H/NaICFTicFoBmXqNluZ+s4kBTnrxDE38QH736u0fHOn3vXFOgmBl7j95lZk3yTpFCJJmkRWR1+S7C5nm3Qa5Fn0QCHSDZd4lxl0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=ACGrXUY3; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="ACGrXUY3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 99A511F000FF; Wed, 30 Sep 2026 19:08:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790795299; bh=ahArGABecHFIxbkQlE1b6IPKZFIonD6LOyiN7taj7Kk=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=ACGrXUY3MlYyd8wGqdFEaqvz8V0+tQCzz+WKhnWY8YeopalbKQT/jKaR/sOJ1yfwI Vsoc7ao78X/BUMHaYzC6mok/KCRZCOQkdfPgHbDj7VSWAyTwqCsNbluFFdTUO6GJXZ Y+o5qbe2vYPnCyX4wC9FrTVwQO7g2AMDzYL3f6FQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Vega , =?UTF-8?q?Toke=20H=C3=B8iland-J=C3=B8rgensen?= , Victor Nogueira , Jamal Hadi Salim , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.6 0511/1193] net/sched: drr: clamp quantum in change class Date: Wed, 30 Sep 2026 17:19:55 +0200 Message-ID: <20260930152445.519957383@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260930152434.301151190@linuxfoundation.org> References: <20260930152434.301151190@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jamal Hadi Salim [ Upstream commit 8382abec0f1568d0a5590d75a3df92f23fcf5196 ] drr_change_class() rejects explicit quantum==0 but falls back to psched_mtu() with no floor. With a crafted size table qdisc_pkt_len reaches ~2 GiB, so quantum=1 (or a zero psched_mtu on a headerless device) makes the deficit-refill loop spin under the qdisc lock. Add clamp_t(u32, quantum, 256, 1<<20) after the zero reject and on the fallback path. The explicit-zero reject is preserved. Conditions to recreate the bug: CONFIG_NET_SCH_DRR=y. Requires CAP_NET_ADMIN (namespace-local via unshare -Urn suffices). tc qdisc add dev dummy0 root drr tc class add dev dummy0 parent 1: classid 1:1 drr quantum 1 Fixes: 13d2a1d2b032 ("pkt_sched: add DRR scheduler") Reported-by: Vega Reviewed-by: Toke Høiland-Jørgensen Tested-by: Victor Nogueira Signed-off-by: Jamal Hadi Salim Link: https://patch.msgid.link/QDISC-0CFC.v3.20260901204856@mojatatu.com.8 Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/sched/sch_drr.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/sched/sch_drr.c b/net/sched/sch_drr.c index 2d468c50137c6..6469b39c91611 100644 --- a/net/sched/sch_drr.c +++ b/net/sched/sch_drr.c @@ -82,8 +82,9 @@ static int drr_change_class(struct Qdisc *sch, u32 classid, u32 parentid, NL_SET_ERR_MSG(extack, "Specified DRR quantum cannot be zero"); return -EINVAL; } + quantum = clamp_t(u32, quantum, 256, 1 << 20); } else - quantum = psched_mtu(qdisc_dev(sch)); + quantum = clamp_t(u32, (u32)psched_mtu(qdisc_dev(sch)), 256, 1 << 20); if (cl != NULL) { if (tca[TCA_RATE]) { -- 2.53.0