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 4B9F1253924; Mon, 23 Jun 2025 13:28:41 +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=1750685321; cv=none; b=YfPBBdQ1VUSxiGCnCHVCWZmHUyWwkomU9/4ye7tw7Sq+dw9jyuJ4Gk9qJxqKJKlpjplQRTK/jr5xXdIWiEEOro4YlaCchKqn0krbutEc/+YA2fUjZrZ76ZuyU6bE/fWiL/0I8a9d1JZG9sfQlaki/9MXpTTBMeXkwaGQQBpBhZk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750685321; c=relaxed/simple; bh=aG28zNqUBQQLhOZTxvrtZlB01S5viv+YMM/ICmXiKvQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Efs0Q7gbTIP3MA8d2hr3LZAQk9f6VQyNeNBum58Iyql+5eU987QK+QQqOUxLmZioXTAC/uBVKWajZBmgNK/4v28q7IqJ7ah+5Ev6yOS9b05iaXufloe9eEr36FakZcKZtglmRr/09txhJGr2kJBhqOMSwphsgZwwHcN7JJ3FEYQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=vdHesvAm; 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="vdHesvAm" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D3EC3C4CEEA; Mon, 23 Jun 2025 13:28:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1750685321; bh=aG28zNqUBQQLhOZTxvrtZlB01S5viv+YMM/ICmXiKvQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=vdHesvAmZyR/rMZYoJPvnCiLam+6yhDl1ZjgojZFW6jUW35XNpGQxOOMqwfRem2VP lAvNVSyzexCQdW3GCFnNGoVvofUhY2yokuXZdmPJGJQkrSxaWBx+P9IAGY9rq3VSrb NLNJuNQEqbroAQMThQj8tv8q7ikvf+DGWTph3Mso= 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 5.4 085/222] net_sched: tbf: fix a race in tbf_change() Date: Mon, 23 Jun 2025 15:07:00 +0200 Message-ID: <20250623130614.658584756@linuxfoundation.org> X-Mailer: git-send-email 2.50.0 In-Reply-To: <20250623130611.896514667@linuxfoundation.org> References: <20250623130611.896514667@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 5.4-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 259a39ca99bfb..9b11e9256336c 100644 --- a/net/sched/sch_tbf.c +++ b/net/sched/sch_tbf.c @@ -394,7 +394,7 @@ 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