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 345B13E40E9; Wed, 30 Sep 2026 18:05:33 +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=1790791535; cv=none; b=GFhtWx9ktVjcceEpc+Us+XWsokN0BcXkaTVN2Xjjnl+ajy2zuXdVzUvcaGFpXD3LC2D5Gv63M79pi9WqumbcWwhW2Ivbdlq0yVYDK5ZpccXZBAbu9+YVkzlA6yM0whodNotli+ypXSpmoex2V1vxkUz4m1aAiZh5S6Cga1nEnbo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790791535; c=relaxed/simple; bh=OMc2KhJ9k4g93wUJUg59XnWB9t6r12D/p156+AW8N0M=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=ub/5jIjjp4qQka8AIcJR5ZX7PEP9qUafB8oGaexpqyPc7aZcCBNzi5K6C0RMF4QHL+zfmiwjfAmiFiLbC3ZEW9R4cvesr0EELl3uw9gR5ZbZLK/77K/nH+ru153l1YCoFuNNtS4PXCdzG/uymK95A6Fmz8o6Nh9ea4yl8fr9/tY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=SrwUgjqz; 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="SrwUgjqz" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5D45A1F000FF; Wed, 30 Sep 2026 18:05:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790791533; bh=0oI1SwUZ8V8japnj2aLp2lhzgVZlvQlPzaCYyF+rErI=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=SrwUgjqzWurZwitgyDaSds40x/9nIWKI6dEwHdbmU0p2ONMJ535McpTxnHEuz9hrm GFkNHNmM/uCHkjiQbds+uhyusxbqz+ZMf9r+lmCWnYq59JIk4I8V+GWvA2CCHRbzzX bInoLkNliwP89Xggg1e9skeyGFd5CWvR27faBxVc= 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 5.15 319/752] net/sched: pie: clamp psched_mtu in pie_drop_early Date: Wed, 30 Sep 2026 17:23:09 +0200 Message-ID: <20260930152405.198682667@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 54370e44c002770ae61fc889f28f699e91616ffc ] pie_drop_early() calls psched_mtu() with no clamp. With mtu=0x80000000 the bytemode divide silently zeroes the drop probability, disabling AQM. Clamp to [1, 1<<20]. Conditions to recreate the bug: CONFIG_NET_SCH_PIE=y. Requires CAP_NET_ADMIN (namespace-local via unshare -Urn suffices). tc qdisc add dev dummy0 root pie tc qdisc change dev dummy0 root pie stab data 32768 size_log 15 cell_log 0 Fixes: d4b36210c2e6 ("net: pkt_sched: PIE AQM scheme") 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.7 Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/sched/sch_pie.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/sched/sch_pie.c b/net/sched/sch_pie.c index ad0d8c892f120..8e35c15092930 100644 --- a/net/sched/sch_pie.c +++ b/net/sched/sch_pie.c @@ -35,7 +35,7 @@ bool pie_drop_early(struct Qdisc *sch, struct pie_params *params, { u64 rnd; u64 local_prob = vars->prob; - u32 mtu = psched_mtu(qdisc_dev(sch)); + u32 mtu = clamp_t(u32, psched_mtu(qdisc_dev(sch)), 1, 1 << 20); /* If there is still burst allowance left skip random early drop */ if (vars->burst_time > 0) -- 2.53.0