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 DE0732EE286; Tue, 17 Jun 2025 16:39:46 +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=1750178387; cv=none; b=lKJh71L3ExJIueUd/cqkB/W+n16Is0TaRW9g0rGapnVkdSr+AeNg/ZcBCIDhv1Uzu1lLSaKTGROoOA1vRYnszaSgulv65lh6If+k2foI68DINJXqjwpWpUipmrpumyq8/Hsrb76V8uqCipTR00EuG1JENgD7TAnmyQhsfi0BI4o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750178387; c=relaxed/simple; bh=wjpFErNYptqf4DP3e7kfki0Qbha79iQK3+SS5iWlFHY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=pVwj3g3tkjOJRv+vTkzdS6w7b5ktSqIyQyys0N02Jtq/UMFiNm8CXhD/UVd7xutdyfRoFuPz9hE4oAjCORCONi4SbQw3MvXDVR4CfhVZvi/eyM5FmFQvMZBBjLF/XxkhYnRPKgN7vxMcYhJgTxp8Vb6SI4V2kRti5u03JA/Pt3E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=N6mYcO73; 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="N6mYcO73" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4B75DC4CEE3; Tue, 17 Jun 2025 16:39:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1750178386; bh=wjpFErNYptqf4DP3e7kfki0Qbha79iQK3+SS5iWlFHY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=N6mYcO73v7701nTNpo3P9FTea/yedJY2jZzdq18xgOZl0rH7Y3KJJTkKCKvZitqmq 44INcube/LDhF2V/Y9I+PN6v5w99Ulx73911LYt7tG1htjQpnYothqK9pZmgjPFr+k q2iYcXM8TY3Ags1ToiVuLfaHIHf8rh28hlWXgquk= 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 6.12 465/512] net_sched: prio: fix a race in prio_tune() Date: Tue, 17 Jun 2025 17:27:11 +0200 Message-ID: <20250617152438.422713431@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250617152419.512865572@linuxfoundation.org> References: <20250617152419.512865572@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 6.12-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 cc30f7a32f1a7..9e2b9a490db23 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