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 D7A473161AD; Thu, 16 Jul 2026 14:07:50 +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=1784210872; cv=none; b=TfY/0AqFs4obF/VxH0SFp6hhrI3NBBDy3t65adVFT7ux2gj1NvlRTGnntH7LfTR0CYCyJwWcFWErtMvkftZytzTtPTvOc1WuYWlFGlD+H88q4aGeS0nCNpKJJ60D15RVCMSkEsqiQfJWdQByxkTXyulAVEBlYmL/rwr1jLJwQ4Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784210872; c=relaxed/simple; bh=+m65FkVTIB5JAk8UEQvkBTUz1Tdltl9aRdEC2wEXRp8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=lAOTS0nuFsC71nLs4w/+2bRTPS+2AKhNZtuLsHTU8e0He6CKgH8KWE5cYG+tM6DKEf1hOfLfqkTvkt8FEfvGEdaEiMIV9L1lb6bThaTB6A4RqWAhqhfob0PhN4E61t//eH/DgMU5kvbMisW/NLjEoK/+snnQyuEXMYi+E8foXwU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=z2cdBhJH; 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="z2cdBhJH" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0F7891F000E9; Thu, 16 Jul 2026 14:07:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784210870; bh=bPb6g+4/cE1/QiKnhj7UTjwgqe/+v2WjaqEjKycJEOs=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=z2cdBhJHirRGlNPIiFeRBNRUYDwa5qsvE1NQ1sdOlhS5+IudGSjYHV6ruP1EUn9x+ pkqy6/Wdk6Hn/EaDz7To/xHEzzvqtoUrrC4NKavMEgbGyGw/cJ9pyVEK7ioZYtVVRX qVNVsl0cBEQLZ8E4FkUIv0U97LrHZtL1cNwOVxN4= 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 6.18 185/480] netpoll: fix a use-after-free on shutdown path Date: Thu, 16 Jul 2026 15:28:52 +0200 Message-ID: <20260716133048.730307384@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260716133044.672218725@linuxfoundation.org> References: <20260716133044.672218725@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 6.18-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 @@ -812,14 +812,6 @@ 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); } @@ -843,6 +835,7 @@ static void __netpoll_cleanup(struct net 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); }