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 CF5523B38A0; Mon, 23 Mar 2026 15:05:51 +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=1774278351; cv=none; b=Pp0uxZOFEyYIQSfOmcRZHjoRTtIwrfXlGwlqJmicGWB10LhTBBze0h6qh0nef1NmY5e8bGw76jdrldCN37rYszogBUX5C1e16sse7DBWHW7UkrdSlwWZUMUd2cg+w7yIdLmSURNTyl5y1NxuSM40vW57F4bDCady8r+EPR4HtAE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774278351; c=relaxed/simple; bh=3znkXsNDAQNsCMYbbi20K7b3FYUrRckS4phDZa9L1as=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ev/nriKUAPziscAv65xc5ZwNXTmWMMn5yN5ce+RuokRvsk141K5umLcnxl6daZo6RumBkNQAMPSr5DBfOtfe+3tCLUc3BqjrqIoW9HrvxQsZ+MyJSF9dCNJlo+HgktmFFGOAlzqZhgZqqx6OQR4eSYhFV9jpt/e0WjBsDwySOlw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=g5DNDGM2; 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="g5DNDGM2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 535EAC2BC9E; Mon, 23 Mar 2026 15:05:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1774278351; bh=3znkXsNDAQNsCMYbbi20K7b3FYUrRckS4phDZa9L1as=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=g5DNDGM2yPru7V4JK7ftKKEeCc4p+a+nIFg8pirdXAFjepzBe6HeBmv68NvszS/AP GRx4qQiyBUiBlmnNM91NeOpVLQvhBc6Sxvy9dJvDCybWYyyhVsUVdhrCavmqbZeBZW wxeRFVDOtXXenKLklqSo9gGbgpyf2T16lnPXkt2s= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Chengfeng Ye , Paolo Abeni , Sasha Levin Subject: [PATCH 6.6 237/567] mctp: route: hold key->lock in mctp_flow_prepare_output() Date: Mon, 23 Mar 2026 14:42:37 +0100 Message-ID: <20260323134539.698700682@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260323134533.749096647@linuxfoundation.org> References: <20260323134533.749096647@linuxfoundation.org> User-Agent: quilt/0.69 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 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Chengfeng Ye [ Upstream commit 7d86aa41c073c4e7eb75fd2e674f1fd8f289728a ] mctp_flow_prepare_output() checks key->dev and may call mctp_dev_set_key(), but it does not hold key->lock while doing so. mctp_dev_set_key() and mctp_dev_release_key() are annotated with __must_hold(&key->lock), so key->dev access is intended to be serialized by key->lock. The mctp_sendmsg() transmit path reaches mctp_flow_prepare_output() via mctp_local_output() -> mctp_dst_output() without holding key->lock, so the check-and-set sequence is racy. Example interleaving: CPU0 CPU1 ---- ---- mctp_flow_prepare_output(key, devA) if (!key->dev) // sees NULL mctp_flow_prepare_output( key, devB) if (!key->dev) // still NULL mctp_dev_set_key(devB, key) mctp_dev_hold(devB) key->dev = devB mctp_dev_set_key(devA, key) mctp_dev_hold(devA) key->dev = devA // overwrites devB Now both devA and devB references were acquired, but only the final key->dev value is tracked for release. One reference can be lost, causing a resource leak as mctp_dev_release_key() would only decrease the reference on one dev. Fix by taking key->lock around the key->dev check and mctp_dev_set_key() call. Fixes: 67737c457281 ("mctp: Pass flow data & flow release events to drivers") Signed-off-by: Chengfeng Ye Link: https://patch.msgid.link/20260306031402.857224-1-dg573847474@gmail.com Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin --- net/mctp/route.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/net/mctp/route.c b/net/mctp/route.c index 009ba5edbd525..59fbc54d8e66c 100644 --- a/net/mctp/route.c +++ b/net/mctp/route.c @@ -267,6 +267,7 @@ static void mctp_flow_prepare_output(struct sk_buff *skb, struct mctp_dev *dev) { struct mctp_sk_key *key; struct mctp_flow *flow; + unsigned long flags; flow = skb_ext_find(skb, SKB_EXT_MCTP); if (!flow) @@ -274,12 +275,14 @@ static void mctp_flow_prepare_output(struct sk_buff *skb, struct mctp_dev *dev) key = flow->key; - if (key->dev) { + spin_lock_irqsave(&key->lock, flags); + + if (!key->dev) + mctp_dev_set_key(dev, key); + else WARN_ON(key->dev != dev); - return; - } - mctp_dev_set_key(dev, key); + spin_unlock_irqrestore(&key->lock, flags); } #else static void mctp_skb_set_flow(struct sk_buff *skb, struct mctp_sk_key *key) {} -- 2.51.0