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 B75ED1DF98B; Mon, 23 Jun 2025 21:14:15 +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=1750713255; cv=none; b=b/zXNu3U3S1l4Dds3MplP1a8kwbup7+LqaBM6m5HIsA3BRt0sq8jHYcGsK6RtMAWtnq+4+3fQhHd+9RAOGy6a1NCxt5yyU7GBi+D9Ev86hHkyKC9Kc9hPJkD8qBBKgr7f1dknEn93C5Y7ERThhOJaCWI+hmcnEKG0DH4NO4VVOc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750713255; c=relaxed/simple; bh=OP3T3NAxnOwIKs4PgVfdhSh2bej4YQaeLM8Kxxxz4r8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=XULwd+Nb2Y/paLUNYy4rHSVRq2XpLmq4VIPf/hLmnEIqipbvcVTwlLy5AqGyEJyNZQXXiAsu/HrMPOO2jw1I7FFlu6Kc7ifBmWC1tLSBUziXY0KAP6mjMA1STBdQF5YxVZ1oyLDprNJ35aW+Zz/rWAqfiYuzibLdxAdT9Txoz9A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Sz9cJhFT; 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="Sz9cJhFT" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 496EFC4CEEA; Mon, 23 Jun 2025 21:14:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1750713255; bh=OP3T3NAxnOwIKs4PgVfdhSh2bej4YQaeLM8Kxxxz4r8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Sz9cJhFTjRk/VSWyfRcppQIki+Yww3e/dYUNW50X4EN4Qgacoaky5ehH/rn+gCdpm A8YsTzKoDYRfFusv2LKKp+9hQxjs/hfOaa7uanxvRDn4Vv+n/Ecws2WY0XYJly60uQ X8YzkLy6i1fFDHZT6AO/oAEoA59W6ErGjQp+QrRM= 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 5.10 134/355] net_sched: prio: fix a race in prio_tune() Date: Mon, 23 Jun 2025 15:05:35 +0200 Message-ID: <20250623130630.760344035@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 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 1c805fe05b82a..3d92497af01fe 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