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 6F54B2EA147; Tue, 17 Jun 2025 16:17:35 +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=1750177055; cv=none; b=CqPVPSkhjOj+GZNZh/UOzNix+iqQstJWsiIoS3FvoxpPcLhJ3ixxPMtUUxEi9If5pgGdIqw0BKY4V1RHDc7REen+RkSdnygEsuoawUGnAZNyg6ojQq8ds6igkHcdiu5qmgYwg0OeD8UQOqoJsH7pmAEo63UUsh9DpsA2rJbSr2Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750177055; c=relaxed/simple; bh=DSJCaVJ65dURo79OC2EpU+Xl8dvqi8j+YZVlCnolhmc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=m9cGOy6jSzRGyPNCEI5Ppp+5V9xE/8Dp6UBNvqsBiNNvMDmGk2x3hFrJ4rNbkeh2uup3y2+v3utHYZTiXhGTl/y+7L6aX2/hF1jNaBPNHNJ+39pJjT4Ts6okKmw4dLecR62CgIT7c0KtfMMP6VEUALu1Qj8bxvISmUTWH11pdL8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=SmNQbb3K; 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="SmNQbb3K" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 74C9AC4CEE3; Tue, 17 Jun 2025 16:17:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1750177054; bh=DSJCaVJ65dURo79OC2EpU+Xl8dvqi8j+YZVlCnolhmc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=SmNQbb3Ke4mQONRytb8HptdJT9e/Ljycl2Mfo6ym1IAWf6soNKZC3EEvg2uMFffy+ hQAFUmDa/ljmXrDmp5p96OjPEtTJwBmr4RzDAlObtu+blWFtt58fgUcO5arTY7neZU JAkKtBbfBRQSaJ3FtZFiCRS73Wamv/TO1sfJ8w8Q= 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 6.6 327/356] net_sched: prio: fix a race in prio_tune() Date: Tue, 17 Jun 2025 17:27:22 +0200 Message-ID: <20250617152351.312150156@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250617152338.212798615@linuxfoundation.org> References: <20250617152338.212798615@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ Upstream commit d35acc1be3480505b5931f17e4ea9b7617fea4d3 ] Gerrard Tai reported a race condition in PRIO, 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: 7b8e0b6e6599 ("net: sched: prio: delay destroying child qdiscs on change") Reported-by: Gerrard Tai Suggested-by: Gerrard Tai Signed-off-by: Eric Dumazet Link: https://patch.msgid.link/20250611111515.1983366-2-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/sched/sch_prio.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/sched/sch_prio.c b/net/sched/sch_prio.c index fdc5ef52c3ee9..fdd9caa41e80f 100644 --- a/net/sched/sch_prio.c +++ b/net/sched/sch_prio.c @@ -211,7 +211,7 @@ static int prio_tune(struct Qdisc *sch, struct nlattr *opt, memcpy(q->prio2band, qopt->priomap, TC_PRIO_MAX+1); for (i = q->bands; i < oldbands; i++) - qdisc_tree_flush_backlog(q->queues[i]); + qdisc_purge_queue(q->queues[i]); for (i = oldbands; i < q->bands; i++) { q->queues[i] = queues[i]; -- 2.39.5