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 B1B471E22E6; Mon, 23 Jun 2025 21:55:29 +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=1750715729; cv=none; b=sBhWF/aw7Liqb3LRqkGZO5+06Le3dF6OeTK1/XpbE/tOgYM7jfQ6E4ZQeh03/EkU8k7A7kVs09DtB4/gK1HU36hb/Sogjnv2k/1rGJMxH96fRXfVaQzPrBhWW2O/+i2ShsRb0FnSWMtQXMZTp4gYdPfcf+KiQJbhbYtM91/ebRg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750715729; c=relaxed/simple; bh=LtwW+5GRnQzfM9SBa/5kAARD5A3BbOWuPrrKOW/NLAY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=qz5VJOgrprMlMo1R4sahW8mKvmooAE8BaNtHKvHDWxZbUuPJNuvZPLnfK7Dpp7nmgm535CijjkoIUa+parKPBfcXPX10BYTLpeeD+MDZ5foN2M5nTi3mPPiU6PdHIM/eSaHNKUqDI2cEh9kTeoGOByst7sHcq1Wo/FIAOr0IdOo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=DMlSLdGj; 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="DMlSLdGj" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EA140C4CEED; Mon, 23 Jun 2025 21:55:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1750715729; bh=LtwW+5GRnQzfM9SBa/5kAARD5A3BbOWuPrrKOW/NLAY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=DMlSLdGjSsfx9vcGTEqs5vesHzB5/XSJtFPgT5+ZqVUoVYqwFStSxEIanPSJtytXM biPReQmypSRfP86SBaP3M37YKEIgZNFX0XCuopRsoHEa0Sv3c0C/IeyaoYOl2J6uUu xIRuWu/UirJyc6+fdGuQD6IvvI8Y1SNiGUd4ycvY= 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 6.1 258/508] net_sched: prio: fix a race in prio_tune() Date: Mon, 23 Jun 2025 15:05:03 +0200 Message-ID: <20250623130651.598400832@linuxfoundation.org> X-Mailer: git-send-email 2.50.0 In-Reply-To: <20250623130645.255320792@linuxfoundation.org> References: <20250623130645.255320792@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 6.1-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