From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 565ED305692; Thu, 16 Jul 2026 14:25:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784211946; cv=none; b=QZiHDHvixj9FpuC7Xg7J09vlGEEAbb49hzemRtMprhfMv10QQr3GeQQ/4Nujr2knBEY5mpo4gjGR5mvDU2hTJa4yFYMDy0ym6RDv7cfU+yqvW4EP2nVtoAu9AoudvnkdmFUYDNlbWlxYUENg7goBKp6TFE+3bTUWDX7ZQJ7b1Ek= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784211946; c=relaxed/simple; bh=JA8/z25v8zvMfXQXRvoH7tgv0frMc4BDNmUxWc+mk6c=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=mMQ/+usG26rovsi+tfSxyhtGDlhEAp2C1XZWwQ4voftBDW2cAPd498av/zIkbojgIoHBIlmijeSD4NJJ+2KHHlXEFp77fuq150xmyUDC5j9uZ9GExerhCXdC54k3fOogHJFTkwAGABZ9/kaJzOgif0MwxjuXAy3zT1Z5BZ5XuXY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=PgZKVT2e; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="PgZKVT2e" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 82ABF1F000E9; Thu, 16 Jul 2026 14:25:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784211945; bh=MPSUY6H7fFB1Gbm8aUycBoZbquWn5hLIx50+9vI6VF4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=PgZKVT2eSsOBCrAuC8nbqxt9oNaEWC6Ie2+t/LsS0nt7LjevS67CmW0NapNKq4IAB 0DfWG5EncVVb9QURGMoM4g8UW2ZVPBv6dV0511hJKrFzSRCoF5gFeLBZ349kDZS5+z LL4f7HkhBLBvq2yCq13+goLh9S/6L7jFIzaXov64= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Pavan Chebbi , Breno Leitao , Jakub Kicinski Subject: [PATCH 6.12 138/349] netpoll: fix a use-after-free on shutdown path Date: Thu, 16 Jul 2026 15:31:12 +0200 Message-ID: <20260716133036.451099416@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260716133033.287196923@linuxfoundation.org> References: <20260716133033.287196923@linuxfoundation.org> User-Agent: quilt/0.69 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 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Breno Leitao commit 45f1458a85017a023f138b22ac5c76abd477db42 upstream. There is a use-after-free error on netpoll, which is clearly detected by KASAN. BUG: KASAN: slab-use-after-free in _raw_spin_lock_irqsave+0x3b/0x80 Read of size 1 at addr ... by task kworker/9:1 Workqueue: events queue_process Call Trace: skb_dequeue+0x1e/0xb0 queue_process+0x2c/0x600 process_scheduled_works+0x4b6/0x850 worker_thread+0x414/0x5a0 Allocated by task 242: __netpoll_setup+0x201/0x4a0 netpoll_setup+0x249/0x550 enabled_store+0x32f/0x380 Freed by task 0: kfree+0x1b7/0x540 rcu_core+0x3f8/0x7a0 The problem happens when there is a pending TX worker running in parallel with the cleanup path. This is what happens on netpoll shutdown path: 1) __netpoll_cleanup() is called 2) set dev->npinfo to NULL 3) call_rcu() with rcu_cleanup_netpoll_info() 3.1) rcu_cleanup_netpoll_info() tries to cancel all workers with cancel_delayed_work(), but doesn't wait for the worker to finish 4) and kfree(npinfo); Because 3.1) doesn't really cancel the work, as the comment says "we can't call cancel_delayed_work_sync here, as we are in softirq", the TX worker can run after 4). Tl;DR: queue_process() is not an RCU reader, it reaches npinfo through the work item via container_of(). Use disable_delayed_work_sync() to ensure the worker is completely stopped and prevent any future re-arming attempts. Once npinfo is set to NULL, senders will bail out and not queue new work. The disable flag ensures any in-flight re-arming attempts also fail silently. In the future, we can do the cleanup inline here without needing the npinfo->rcu rcu_head, but that is net-next material. Cc: stable@vger.kernel.org Fixes: 38e6bc185d95 ("netpoll: make __netpoll_cleanup non-block") Reviewed-by: Pavan Chebbi Signed-off-by: Breno Leitao Link: https://patch.msgid.link/20260625-netpoll_rcu_fix-v2-1-0748ffac1e98@debian.org Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- net/core/netpoll.c | 9 +-------- 1 file changed, 1 insertion(+), 8 deletions(-) --- a/net/core/netpoll.c +++ b/net/core/netpoll.c @@ -899,14 +899,6 @@ static void rcu_cleanup_netpoll_info(str container_of(rcu_head, struct netpoll_info, rcu); skb_queue_purge(&npinfo->txq); - - /* we can't call cancel_delayed_work_sync here, as we are in softirq */ - cancel_delayed_work(&npinfo->tx_work); - - /* clean after last, unfinished work */ - __skb_queue_purge(&npinfo->txq); - /* now cancel it again */ - cancel_delayed_work(&npinfo->tx_work); kfree(npinfo); } @@ -930,6 +922,7 @@ void __netpoll_cleanup(struct netpoll *n ops->ndo_netpoll_cleanup(np->dev); RCU_INIT_POINTER(np->dev->npinfo, NULL); + disable_delayed_work_sync(&npinfo->tx_work); call_rcu(&npinfo->rcu, rcu_cleanup_netpoll_info); }