From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 39D413FFAA2 for ; Fri, 15 May 2026 09:24:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778837049; cv=none; b=E89fRonzNQogpbIlRBOjc2ohcPy9U24+NMDH5cebv7BYcfcC/9+/Z1aNEO+qoc5Xs6c5C8rID/+1q1YsMa20gssRqMCGCQGpOfEY9D6OAIBo50WS4TyV5GwoBVD3zoVqqimUOhxK45aNEzOCzZ4m4311rXC7EM+YdKsrBLRUwEQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778837049; c=relaxed/simple; bh=Bp6CWGsou7BAV6pGfQtdLnSzoLmHA716Y07kxD7QWvQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=gF9qIqy3ZJI7bE6vaVVpfFT4sZt4bM1EPXpRxvw/6RRmNH1BmPuc+FECkZC2+C/ivnv1gw6MHedbr1hqW/wie84HJVWRgSrSH0hg9Glmj+KLi5HteHMRVoFMtXpuZxTn4yAcYkROVyQqfncD3jubLZVbgWws8LN/S6JxS30OCI8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=T4D6PHH8; dkim=pass (2048-bit key) header.d=redhat.com header.i=@redhat.com header.b=VV4GVdWO; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="T4D6PHH8"; dkim=pass (2048-bit key) header.d=redhat.com header.i=@redhat.com header.b="VV4GVdWO" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1778837047; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=8Jiq1OelULddFb2fRbTl+saaV/R1Ybw5/2bXhzK6jPA=; b=T4D6PHH8ssRRfysYMyCwTdv2lNzmuyz6O7Ybx/Njhwn1q4S1oZvsAUocX/ubIxKoFRgLDi YVC1k362jLBGhETNvFzbp28h9AVGZ8JBY5pn9gnR2egP9YfKIn2FcPUnSxwUeO5fh1VBy0 4CzdkP+BWHbJ7DuJBavstSUhQIMpNHw= Received: from mail-wm1-f69.google.com (mail-wm1-f69.google.com [209.85.128.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-601-Z3h9zIeoPz-77fkQyKHH0g-1; Fri, 15 May 2026 05:24:05 -0400 X-MC-Unique: Z3h9zIeoPz-77fkQyKHH0g-1 X-Mimecast-MFC-AGG-ID: Z3h9zIeoPz-77fkQyKHH0g_1778837044 Received: by mail-wm1-f69.google.com with SMTP id 5b1f17b1804b1-48fdacff6d2so13157035e9.2 for ; Fri, 15 May 2026 02:24:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=google; t=1778837044; x=1779441844; darn=vger.kernel.org; h=content-transfer-encoding:in-reply-to:content-language:from :references:cc:to:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=8Jiq1OelULddFb2fRbTl+saaV/R1Ybw5/2bXhzK6jPA=; b=VV4GVdWO9LUcEI19YKVBSvQxPcP5fW0dDTLlP7DAIpK6wuuLUNIo59uZVlNcsoM+SN 8w6kWCOon9R68xmSKGG+lHxXGu5FhrPWcruwOpaU/S/GPGKFoygcBg6oCXpTeFLa5KKs 8TXPEWCNAlt658ymntf+lA0eoAtUSEavzOTk+bNendokUjoU7gzhgfTaVk5DMab5Juux GNugVtOUEvplP4Xx7gSLUaZpOK7sjODR9mXvRqcLph/nRNsaGr+GLpQZJwSmcAojxBmD Gbv9vSf/hYPds66DjS4UszCV76F+cQKzabSYJQ4tMIOMAuVr7+U6XbrHa5EfT0Ag9Qj8 qPvg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1778837044; x=1779441844; h=content-transfer-encoding:in-reply-to:content-language:from :references:cc:to:subject:user-agent:mime-version:date:message-id :x-gm-gg:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=8Jiq1OelULddFb2fRbTl+saaV/R1Ybw5/2bXhzK6jPA=; b=crCA1w3tFcecd8r87xYkYWllhFIRIRvwjnazFNtJz6HvovngGjKPQ0GN7drQQO6Nvx N/u8FzbnE+DR+8dW2JfPpF4goz5k38lTKRSg/rFr4JtSEYc+m3p9E59pF9D38f2AhXFv 1mo9SB18YhqEG5/eDuP7g1Ft/VpO65AWiF6In82maGtsRr3ThQUYE7bBXXIswBfvKyZV 0MBxSYROCP2hP+xr2T988+0ouJ7DLl0Zfi3B2ECjRGh4BUbEo7JOx0zOv3bCzylyTurX 8N8MZxjtL+Pfc8/Q3cMNNMPZHt5ZnwIRx0jrMDSQ3AUxvXMndpX31QTFq0KRPXTPZebv r4rg== X-Gm-Message-State: AOJu0YyiUjCPV9O+t1TNpiRzZY8UlUetkzySEZPmrbBsW89hhKNl3mAx ILRI8ugtYS7/+sxxPSr3lWcGqpjqfGC9R2e6fcJVJCDTMcaFeeyWzHpfYRzXkyLW8cLiHkvL346 Gd7Pm4F3AqcpNGr3bOdjqwvTIcCt8qSQ6SPNPWOw1/xthZRuZXuCOKMesBQ== X-Gm-Gg: Acq92OF2JmUgkot9ArVm3Youu+0j7JmUsmVc4g0iHdI35DJdx+A7/b+XuZfWIZ3N08R JBtw6DdmYHDNYXO4hmZ7XzX59rHtQeOxm9D/LmocPdCYmwOsK/QqWIHq4v6mD7HwVoLR/hdIle6 0vppsH7sVZHAKtLLC1tovjJqxeBxdaH/ff5ROow9ySnAijMUq7/doAyBZ5YH0tGw0h/PcGwIfbg qASMcogitHqLJwyvPGs5LCPaWjA7cQzcUCcyeXeHhr88E7QBDdQ2/hKxV5lTnzmXdAIBCbWNlGr E2+iQtwsU6oOg62i+WhM9L/7oYLtY0+PihyWjn5DcwVWxPqyu8dF5TzAwJPhklQOJeSWVF0GBnB ZZpNUQomuGT67mz8mxNXunBq6uKDS6hT2TF7pZIPzHwd8BfRBwUjJ1BoAwg== X-Received: by 2002:a05:600c:a00f:b0:48a:52f2:a0f1 with SMTP id 5b1f17b1804b1-48fe63263eamr42397785e9.18.1778837044047; Fri, 15 May 2026 02:24:04 -0700 (PDT) X-Received: by 2002:a05:600c:a00f:b0:48a:52f2:a0f1 with SMTP id 5b1f17b1804b1-48fe63263eamr42397425e9.18.1778837043649; Fri, 15 May 2026 02:24:03 -0700 (PDT) Received: from [192.168.88.32] ([212.105.155.231]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48fe57944c1sm56922025e9.7.2026.05.15.02.24.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 15 May 2026 02:24:03 -0700 (PDT) Message-ID: <36ffcd43-ebda-44d8-9e32-4268826deb49@redhat.com> Date: Fri, 15 May 2026 11:24:01 +0200 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net] net/stmmac: Fix free-after-use panic when interface goes does with XDP To: Jakub Raczynski Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, mcoquelin.stm32@gmail.com, alexandre.torgue@foss.st.com, k.domagalski@samsung.com, k.tegowski@samsung.com, Chang-Sub Lee References: <20260511165045.3091475-1-j.raczynski@samsung.com> <4ca19ae1-6606-433b-9860-0a8cce12f80f@redhat.com> From: Paolo Abeni Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 5/15/26 10:29 AM, Jakub Raczynski wrote: > On Thu, May 14, 2026 at 02:01:20PM +0200, Paolo Abeni wrote: >>> >>> Fix this by following: >>> - Set STMMAC_DOWN flag before stopping DMA to signal XDP to stop >>> - Call synchronize_rcu() after stopping DMA but before freeing resources to >>> ensure all ongoing NAPI operations complete >>> - Add STMMAC_DOWN flag checks in XDP code paths (XDP_TX and XDP_REDIRECT) to >>> drop packets when interface is going down. This has already been done for >>> stmmac_xdp_xmit() so make it consistent >>> - Clear STMMAC_DOWN flag in __stmmac_open() to restore normal operation. >>> This was only done for stmmac_reset_subtask() during abnormal operation, >>> which is not enough. This does not affect normal operation as this flag is >>> used only for XDP apps >> >> The above looks racy. I think instead you should just use >> napi_synchronize() in __stmmac_release. >> > You put this after whole section, but I assume you are talking about > synchronize_rcu()? Because currently there are 0 checks and it is pure race > condition. synchronize_rcu() does secure it in some way, but you are correct, > proper ensuring that napi has finished is napi_synchronize(). > Will fix in v2. >> >>> @@ -5267,6 +5279,9 @@ static int stmmac_xdp_xmit_back(struct stmmac_priv *priv, >>> if (unlikely(!xdpf)) >>> return STMMAC_XDP_CONSUMED; >>> >>> + if (unlikely(test_bit(STMMAC_DOWN, &priv->state))) >>> + return -ENETDOWN; >> >> Sashiko noted here you should return STMMAC_XDP_CONSUMED >> >> /P > Seems good, will fix in v2. If you use napi_synchronize(), I think you can avoid setting STMMAC_DOWN and testing it in the fast path: the run-to-completion after irq disabling should ensure that no tx could happen after that napi_synchronize() completes. Side note: it's not clear to me where/when irq disabling take place?!? /P