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 24C2B434E4B for ; Mon, 13 Jul 2026 13:53:33 +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=1783950814; cv=none; b=JBzEpWsONFfOISNdMZose0WhpUbtGAt3iVR4TPklvp7G1q+al8xrc38lar16CrwdpV8nV+cI6WiVabaPd+rZXr7tXORzqmaId6XYKu57I4oaQ1pTUNHGLcmVJ0GMHJCoEsyqbmqZ12SXgNyu7nVVQeN0PcgVbfC+rOt0jqdXqrM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783950814; c=relaxed/simple; bh=S1xKfgeIFWG1s5VdaMDGPoJESbsuJi159VmFumETu94=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=UcUPvfxr+ua07EBS/Sy0HQk2UkqXB/6SVRiTYPsfw2PzUDVXMEXSYUs/fbjBG7KpZeQwPo1EYHQboDaU7sYRc4mGdE/Dcl/Zogy3qhpPJtTEw7C6uZwkYvkS0yKczqkAqP7jAytcvm2zpqw1mqL59xbLbBM71rJ6fK5nDe8kPFY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=LDnf59Hd; 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="LDnf59Hd" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8A2ED1F000E9; Mon, 13 Jul 2026 13:53:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1783950813; bh=7DWlsb3D6+50zHbBjUbhuGfSBfWlu84n/coGuYmuIjQ=; h=Subject:To:Cc:From:Date; b=LDnf59HdT5Qz4Ju3otxfKKK5jS1hATl6fbxxuWCctAV8kU44udgtINIJ8EzCkP8zl Cqcpr1uaRJQFMuYjjHoy436oFlmXuMTRvPCzGO9rbTGIZQ+K8sE9GLQv8ykHoL/0yX zGqNB/MyrfccS3m1fFcLpOLNn75LFONq3Uy+m59o= Subject: FAILED: patch "[PATCH] netpoll: fix a use-after-free on shutdown path" failed to apply to 5.15-stable tree To: leitao@debian.org,kuba@kernel.org,pavan.chebbi@broadcom.com Cc: From: Date: Mon, 13 Jul 2026 15:45:50 +0200 Message-ID: <2026071350-embark-gave-c0f4@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x 45f1458a85017a023f138b22ac5c76abd477db42 # git commit -s git send-email --to '' --in-reply-to '2026071350-embark-gave-c0f4@gregkh' --subject-prefix 'PATCH 5.15.y' 'HEAD^..' Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 45f1458a85017a023f138b22ac5c76abd477db42 Mon Sep 17 00:00:00 2001 From: Breno Leitao Date: Thu, 25 Jun 2026 05:03:18 -0700 Subject: [PATCH] netpoll: fix a use-after-free on shutdown path 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 diff --git a/net/core/netpoll.c b/net/core/netpoll.c index 229dde818ab3..96d5945e6a30 100644 --- a/net/core/netpoll.c +++ b/net/core/netpoll.c @@ -633,14 +633,6 @@ static void rcu_cleanup_netpoll_info(struct rcu_head *rcu_head) 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); } @@ -664,6 +656,7 @@ static void __netpoll_cleanup(struct netpoll *np) 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); }