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 20BB21E51FA; Mon, 23 Jun 2025 21:27:30 +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=1750714050; cv=none; b=ERMyKUE2QS24Qw210FrX2mZIhwQkyYu0Ym13/syOQ+9Jpiyt+mBHpJ2ejaUeQKmcoLvEHEYmSbkTIz0e8exZdfcdFSZ5sExIJPlVllRUqYaJ6Vw4fh4mG5Jv7pXjmKnpA865zkcZUvlZJcwUp1u6oaC7l1vuOlgj5Et7oDiEftA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750714050; c=relaxed/simple; bh=NmcXHfJHKz4CH0mvhJdI/D8IBE5cqimV2TvEOeezJMk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=X7gbPJ0duHfaZSOJnTzVNRHbgD1XRjga54adKEQL5yVweWdm8Fqi8ISgOt4VdfINLTloijtPQ0bQ1T0G7cHWAQDwEi9VsGPHF2stkY9xIGlK0r2ZyJkyCOjW/fr4O6u28/pC28wQHW22DngEb/D4AAyrVnE1oBj9o2Zu0/FEU+Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=gL/uUnpV; 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="gL/uUnpV" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AB9F3C4CEEA; Mon, 23 Jun 2025 21:27:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1750714050; bh=NmcXHfJHKz4CH0mvhJdI/D8IBE5cqimV2TvEOeezJMk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gL/uUnpVLniZK+jDyUzqRPG0X4NxjGeCGQFTILFe8kylPRY5uou/dzVtCBabHAv1N 7QLaB5IAFn1U0Ps8UKyXmHVLo1SP8Ont0yOlRc8HAM4GVkw2YHTpbxme6+Mys6JGf1 CU6//4+qSNkbBM7Gc58RegjCrvOXXaxnQPabC98s= 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 5.15 162/411] net_sched: ets: fix a race in ets_qdisc_change() Date: Mon, 23 Jun 2025 15:05:06 +0200 Message-ID: <20250623130637.731511765@linuxfoundation.org> X-Mailer: git-send-email 2.50.0 In-Reply-To: <20250623130632.993849527@linuxfoundation.org> References: <20250623130632.993849527@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 5.15-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 a37979ec78f88..b49e1a9775865 100644 --- a/net/sched/sch_ets.c +++ b/net/sched/sch_ets.c @@ -675,7 +675,7 @@ 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); } q->nstrict = nstrict; memcpy(q->prio2band, priomap, sizeof(priomap)); -- 2.39.5