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 1F8D01DF98B; Mon, 23 Jun 2025 21:14:55 +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=1750713295; cv=none; b=dRBaYyBhyKCpOjsxkWGo4TAf0ntd+nXpLRVOMQ6L04wS9dMStFr7XLlG1i61sy7IgX1gVhnTwSVqYuAu3donM61AP35pA3HXzJndCNPSIsmMl8nE5A6rlEt9C/vjVGtd63K7OI007iIcQcf87ZIFEextGRQLNgVLt2I1NVZqOnU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750713295; c=relaxed/simple; bh=W2IMrvAhIw6PRIU1quIoLnScn17fgYrMqiSTILdMRd0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=TK4q8JQW9PTClOSPO8yfpXPPlCKZQiAwx/gmm2T1Ji76lUCmPAu9r0MR/ZMBMrPgsMbyi9pMIPFj6OOuDZr8fvEreLi+hEkfx1NA4ST/NLm12PNGfD8R4U0dOubKbXTQY0+vsrcKqmkeoTe9PUxUOFa6TFN+yu3yFsEpvrkOEWg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=BYUOUYTo; 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="BYUOUYTo" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AB1E3C4CEEA; Mon, 23 Jun 2025 21:14:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1750713295; bh=W2IMrvAhIw6PRIU1quIoLnScn17fgYrMqiSTILdMRd0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=BYUOUYToqnezMWlaGvT14EbSRNnHW7CT3iJYpKvw6WY9wN+I0zD3HXlgBP1PoEadx WVjVtla+7MgaEhGfjwybKB1WYBpRCKC4k7yBGb1YRu+lpe2X0iVUyqpYb538r5hTWZ JLPk5NZvDTWuSoumsPF03IBn2jFJToRH7cqZF1s4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Gerrard Tai , Eric Dumazet , Zhengchao Shao , Jakub Kicinski , Sasha Levin Subject: [PATCH 5.10 136/355] net_sched: tbf: fix a race in tbf_change() Date: Mon, 23 Jun 2025 15:05:37 +0200 Message-ID: <20250623130630.817107728@linuxfoundation.org> X-Mailer: git-send-email 2.50.0 In-Reply-To: <20250623130626.716971725@linuxfoundation.org> References: <20250623130626.716971725@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 5.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ Upstream commit 43eb466041216d25dedaef1c383ad7bd89929cbc ] Gerrard Tai reported a race condition in TBF, 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 Cc: Zhengchao Shao Link: https://patch.msgid.link/20250611111515.1983366-4-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/sched/sch_tbf.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/sched/sch_tbf.c b/net/sched/sch_tbf.c index 5f50fdeaafa8d..411970dc07f74 100644 --- a/net/sched/sch_tbf.c +++ b/net/sched/sch_tbf.c @@ -437,7 +437,7 @@ static int tbf_change(struct Qdisc *sch, struct nlattr *opt, sch_tree_lock(sch); if (child) { - qdisc_tree_flush_backlog(q->qdisc); + qdisc_purge_queue(q->qdisc); old = q->qdisc; q->qdisc = child; } -- 2.39.5