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 3565238DC66; Wed, 30 Sep 2026 18:06:05 +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=1790791566; cv=none; b=W2s5gf2/DXlR9b4eNt/OUVV4UyAJRCBiCFkvc5zYpZ/dMTzZ1g683LSufPJnE8dunpxKxgUlI5BFKy3jofSvamObUfDmK4A0RWofitHSiqFK+O4PuM5XN5v7VEoGUj49BzPTJdG13oNUFXbippV5bQkO5+hSE2us0Jvj38HigtM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790791566; c=relaxed/simple; bh=FZAjIiJ/fv8cn55kwx3uU8je30VWIQh0zxKFvVwfXBw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=UCHAbPZiXSb1l+SSXK+Pi+mUyJHOgMD2tBjF6S3uni+f7PzBGHODcNrdEsBi1N5moGy1/dh2J+3nXfmVw7AcSbul0GGKdEolt5G4aSDGZDxgGFabgYxwolV55TZ1WzaSgzQ5AyKd5KJj+RXYEnk9sd5DgYaUsteQMurfDXToOKs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=mSJbedez; 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="mSJbedez" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 93B9A1F00898; Wed, 30 Sep 2026 18:06:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790791565; bh=NQ+P5lM7EQoGfg8cTCsyvpx2NTLWaJVt3SJQjx+0hm8=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=mSJbedezUU/XWUDXOZyvdxIzTxKiqXkMbBFl4OLdCln/ZS/04EeCJcuGknL8AwZO1 APJoScLqJSrr8gf/sdAbLCQG/+n5BWPCL+nQRDF/SW/uYBXiAsWOYtQRl4NgAWMJGA ZsjWwuZ7rePEBOL4enitH0jJNwiZ3jkxwvzSfHGQ= 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 5.15 320/752] net/sched: drr: clamp quantum in change class Date: Wed, 30 Sep 2026 17:23:10 +0200 Message-ID: <20260930152405.220841077@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260930152358.131179731@linuxfoundation.org> References: <20260930152358.131179731@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 5.15-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 01198fe915052..485541a23b5ba 100644 --- a/net/sched/sch_drr.c +++ b/net/sched/sch_drr.c @@ -83,8 +83,9 @@ 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