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 7ED4D4DEC3F for ; Thu, 17 Sep 2026 16:15:05 +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=1789661707; cv=none; b=G6yZZfvHCbnFGsNz+ZvXSYFdn5EoZZlNnlZoIco7RgxaxfisFR/9xcrYD9roIHCXGjnlyHcxrHyzuT8V2dNHMQC48yM0Sd8H3zR8gQJVTC7+DPmv3OS3Hi6ZiWD8AuLQU7GGllRdJ0ulr5CoKXxBuaYzuR9kQB5kfdtDLcH6SXI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789661707; c=relaxed/simple; bh=nWU8aT2zIi9aS70mtuFjeatq0WQ8uKpdWkm/BaqxhYk=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=shu+ISYWmslVmhDip/Q+/5jDasMd5FFkseRRx/AZw+qQbNb8k3r2YExSPMmdxpUqClOi4wF2WEcf2LjDdRd65EOspYgeabxzkX3PcVyfm6KdhTLvk/3V9RNfPw1iTqCZdbVJQChPfqQT2yv4AMYzYtkIPMhIckHkeVG6GujDeTA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=J6/579tk; 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="J6/579tk" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D29831F000FF; Thu, 17 Sep 2026 16:15:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789661705; bh=SyORisvT+xWeLrhOeF2LAOJ4vPO04twi4zFKDtUpE4s=; h=From:To:Cc:Subject:Date:Reply-To; b=J6/579tkXz6mqYhvGdJ1oJjkCrJtKeQVOZi+71oNXUelSqjFWq2ldjb3pg6zdTwp6 g21vZxyzKyTW2rzS+LioEON9GwbJL+6fLVN8XCjUaLXXJC9l28uEPrIQwV5pJTw3MD cSaz3TqyJ3rElL+1/KQYRezYSarOzawqV7SRVWq4= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-90109: net: sched: fix 32-bit backlog wrap in gred, bfifo and plug enqueue Date: Thu, 17 Sep 2026 17:08:59 +0100 Message-ID: <2026091715-CVE-2026-90109-e297@gregkh> X-Mailer: git-send-email 2.55.0 Reply-To: , Precedence: bulk X-Mailing-List: linux-cve-announce@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3625; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=Ub3YyOpeG/3L1wFxepL+7Kj40hIxNlUPblsTyGG+kBo=; b=owGbwMvMwCRo6H6F97bub03G02pJDFlrBPKf9vt63H62+57tpK27FhSf53l8am6sueTxqzeVl 3C5O5fc74hlYRBkYpAVU2T5so3n6P6KQ4pehranYeawMoEMYeDiFICJyLxgWDB/ypLJgdwLTFS+ Nv5dc1Bs85k9d6wYFqwN5FR2rLJ+dK/xvPw3eZZ5ix5oVgEA X-Developer-Key: i=gregkh@linuxfoundation.org; a=openpgp; fpr=F4B60CC5BF78C2214A313DCB3147D40DDB2DFB29 Content-Transfer-Encoding: 8bit From: Greg Kroah-Hartman Description =========== In the Linux kernel, the following vulnerability has been resolved: net: sched: fix 32-bit backlog wrap in gred, bfifo and plug enqueue gred_enqueue(), bfifo_enqueue() and plug_enqueue() admit a packet when the current backlog plus the packet length fits within the queue limit: sch->qstats.backlog + qdisc_pkt_len(skb) <= sch->limit (gred default VQ) gred_backlog+qdisc_pkt_len(skb) <= q->limit (gred configured VQ) sch->qstats.backlog + qdisc_pkt_len(skb) <= sch->limit (bfifo) sch->qstats.backlog + skb->len <= q->limit (plug) sch->qstats.backlog and q->backlog are u32, and qdisc_pkt_len()/skb->len are unsigned int, so all sums are computed in 32 bits and wrap at 2^32. Once the true backlog exceeds 4 GiB the wrapped sum becomes small and admission keeps succeeding, so the queue grows without bound and the kernel can be driven to OOM. Promote the sums to u64 so admission stops once the true backlog exceeds the limit. The limit is u32, so the bounded queue stays below 2^32 and the stored u32 backlog never wraps. The bug can only be reproduced as root (albeit with ridiculous setup): attach a gred (or bfifo/plug) qdisc with a limit near 4 GiB, leaving the default VQ unconfigured (for gred), and drive >4 GiB of queued traffic (e.g. via a size table / stab to inflate qdisc_pkt_len, or sustained high-rate traffic). The u32 backlog+len sum wraps at 2^32, admission keeps succeeding, and the queue grows unboundedly to OOM. The Linux kernel CVE team has assigned CVE-2026-90109 to this issue. Affected and fixed versions =========================== Issue introduced in 4.2 with commit a3eb95f891d6130b1fc03dd07a8b54cf0a5c8ab8 and fixed in 6.12.110 with commit 3fb51b3960342bbee563543f8d33710fd0fb5a96 Issue introduced in 4.2 with commit a3eb95f891d6130b1fc03dd07a8b54cf0a5c8ab8 and fixed in 6.18.52 with commit 8b2d8c70b969bf84f9e248bfaf2a7135129f2eb6 Issue introduced in 4.2 with commit a3eb95f891d6130b1fc03dd07a8b54cf0a5c8ab8 and fixed in 7.2.6 with commit d98b92f3d57976ae185238946ec5ea0be32195aa Issue introduced in 4.2 with commit a3eb95f891d6130b1fc03dd07a8b54cf0a5c8ab8 and fixed in 7.3-rc1 with commit 4c660ee8c809637909f4f7eb1017f7b9401c75c4 Please see https://www.kernel.org for a full list of currently supported kernel versions by the kernel community. Unaffected versions might change over time as fixes are backported to older supported kernel versions. The official CVE entry at https://cve.org/CVERecord/?id=CVE-2026-90109 will be updated if fixes are backported, please check that for the most up to date information about this issue. Affected files ============== The file(s) affected by this issue are: net/sched/sch_fifo.c net/sched/sch_gred.c net/sched/sch_plug.c Mitigation ========== The Linux kernel CVE team recommends that you update to the latest stable kernel version for this, and many other bugfixes. Individual changes are never tested alone, but rather are part of a larger kernel release. Cherry-picking individual commits is not recommended or supported by the Linux kernel community at all. If however, updating to the latest release is impossible, the individual changes to resolve this issue can be found at these commits: https://git.kernel.org/stable/c/3fb51b3960342bbee563543f8d33710fd0fb5a96 https://git.kernel.org/stable/c/8b2d8c70b969bf84f9e248bfaf2a7135129f2eb6 https://git.kernel.org/stable/c/d98b92f3d57976ae185238946ec5ea0be32195aa https://git.kernel.org/stable/c/4c660ee8c809637909f4f7eb1017f7b9401c75c4