From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 E5E732FA623; Tue, 17 Jun 2025 16:55:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750179352; cv=none; b=tBHuHe+4VF/N7cAKWrA9By0HTU8i5JAN5/npKzlVry02LRX05rmXiBNVrYkeFI9kJ1cLbijfLrDFHVzYVxNhsfItkwzf+gk0YQIbXHzn84tLk7/kNOo/3Avw3KsM/iAl1M5epSMrE2qklaKNrp42MAjYfiWUkNGSnN/6F5QRA38= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750179352; c=relaxed/simple; bh=lAxVx16948iwgSsnJ7QQbs267rg/Cvkt3QnTryo2l0Q=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=mMfbDayydcwYz/aNbZlZvVvC5GVuiupTqiT8pAsi8Pr05Mlzoz6bhRsdPqpC/2iRwk63fc+9p3IAOfZnUWKeabgjpvuNfnKvHG2Pu6lnsblbQzf9DEsBe0C0cfzzCghtgzwLWN+jOE6nXPVSF711KdW4k8Rd6p/ZSwOmgU1GiqU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=lCGbu5HC; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="lCGbu5HC" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 536AEC4CEE3; Tue, 17 Jun 2025 16:55:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1750179351; bh=lAxVx16948iwgSsnJ7QQbs267rg/Cvkt3QnTryo2l0Q=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=lCGbu5HCnML1SFgIdcpxNiudRdNOo4Rru1caWxkfATb4wQ86SrgqczgdH62Juvoyq wue298Sr0l5aTeMSfwHsJAaWvxgM0hofPlTjahqhrXJ75CDe5wvTQ5XjpFKhdlb9CU 98GM3ZwI5UgyE/horE2g9KjvSwxo6ZHfIlQIuY9E= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Gerrard Tai , Eric Dumazet , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.15 720/780] net_sched: ets: fix a race in ets_qdisc_change() Date: Tue, 17 Jun 2025 17:27:08 +0200 Message-ID: <20250617152520.815870526@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250617152451.485330293@linuxfoundation.org> References: <20250617152451.485330293@linuxfoundation.org> User-Agent: quilt/0.68 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-Transfer-Encoding: 8bit 6.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ Upstream commit d92adacdd8c2960be856e0b82acc5b7c5395fddb ] Gerrard Tai reported a race condition in ETS, whenever SFQ perturb timer fires at the wrong time. The race is as follows: CPU 0 CPU 1 [1]: lock root [2]: qdisc_tree_flush_backlog() [3]: unlock root | | [5]: lock root | [6]: rehash | [7]: qdisc_tree_reduce_backlog() | [4]: qdisc_put() This can be abused to underflow a parent's qlen. Calling qdisc_purge_queue() instead of qdisc_tree_flush_backlog() should fix the race, because all packets will be purged from the qdisc before releasing the lock. Fixes: b05972f01e7d ("net: sched: tbf: don't call qdisc_put() while holding tree lock") Reported-by: Gerrard Tai Suggested-by: Gerrard Tai Signed-off-by: Eric Dumazet Link: https://patch.msgid.link/20250611111515.1983366-5-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/sched/sch_ets.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/sched/sch_ets.c b/net/sched/sch_ets.c index 2c069f0181c62..037f764822b96 100644 --- a/net/sched/sch_ets.c +++ b/net/sched/sch_ets.c @@ -661,7 +661,7 @@ static int ets_qdisc_change(struct Qdisc *sch, struct nlattr *opt, for (i = q->nbands; i < oldbands; i++) { if (i >= q->nstrict && q->classes[i].qdisc->q.qlen) list_del_init(&q->classes[i].alist); - qdisc_tree_flush_backlog(q->classes[i].qdisc); + qdisc_purge_queue(q->classes[i].qdisc); } WRITE_ONCE(q->nstrict, nstrict); memcpy(q->prio2band, priomap, sizeof(priomap)); -- 2.39.5