From patchwork Tue Aug 25 09:16:27 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?b?QmrDtnJuIFTDtnBlbA==?= X-Patchwork-Id: 1350916 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming-netdev@ozlabs.org Delivered-To: patchwork-incoming-netdev@ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org (client-ip=23.128.96.18; helo=vger.kernel.org; envelope-from=netdev-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256 header.s=20161025 header.b=dKNfoIko; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by ozlabs.org (Postfix) with ESMTP id 4BbNfl6d7bz9sSP for ; Tue, 25 Aug 2020 19:17:03 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729357AbgHYJQ6 (ORCPT ); Tue, 25 Aug 2020 05:16:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40120 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728717AbgHYJQv (ORCPT ); Tue, 25 Aug 2020 05:16:51 -0400 Received: from mail-pg1-x542.google.com (mail-pg1-x542.google.com [IPv6:2607:f8b0:4864:20::542]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 35D5EC061574 for ; Tue, 25 Aug 2020 02:16:51 -0700 (PDT) Received: by mail-pg1-x542.google.com with SMTP id o5so6392181pgb.2 for ; Tue, 25 Aug 2020 02:16:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=b4uiR7mjiUEO8q/J67JSbBTgAuzIsuSUAuOtPzxxrK0=; b=dKNfoIkozlHWaHujT1mzqUPk6evaug7/VktNscdnpKS8wZ/CBMC4y5tJMkqWEPP2j+ 6wxF+ohJeaTMM9zH352iYNj3pSsHGRXa2WujPLqbL09to6lJMpB9bNlKhhC6J7BDQk8k Zt7FeRz+2LtfI0T8UnGbtoX4D+a5tWBcuLtcsWol+qbi+KzAD49u64bFvKPk5yFZg40T VVBMEX9MAmPOeY3g5Fs06i7L/ldJAJviDFmpXAMM78bcUDi1CyVRv58F56juIhS15tr5 jVy2ITGI8zWoao23JxAFaatZkbv4Qgej+jjP49hfX0MclsWpPrytaegs9uTA0AogMnPw EnLA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=b4uiR7mjiUEO8q/J67JSbBTgAuzIsuSUAuOtPzxxrK0=; b=E69Cz6czF8/5RJ0CrHsNJsy/6v3eU+KmMFSBpTNqBtE0sNhaQgdEeidHTW1TZEZwSP SsWYrNdp8FwFkGighpswhMasJqfYrjVO6UQmSa9N/U6XGNPonudJPmtI5odhOoKfP7pc hxuflFHRq5wXy0FIi2Kb/QW/BTwkGj9pvvE9cXQr/XBWz8tKp+WLksutdI1WX6ILVzpC I5UlvsPbylgjQVIscyVnJG4Q1/wjvSZhCzHDiTexU3P92/0fpGbClgHqiePX1k4bocuZ W1O1MZkKqukNRvNqtcCFfTMyieJLLNx7HQRe0RlEXps/k6xa+9VFWOhjnspF2dZ9vhEl pRWw== X-Gm-Message-State: AOAM530tksy/Kk8u3ihrt0bqWBk4Ucnhe2ffQHnIMP3lgWxysZU5VoyQ GvVITauRV5KSc4zuHB3QaqY= X-Google-Smtp-Source: ABdhPJzHBBNilV6r/snjUSKwBGOSJHXBrAS2V/2nBmJVpI8OLkFynozFebZswPvi4RWt2aDmbn9w+A== X-Received: by 2002:a17:902:6bc6:: with SMTP id m6mr6899554plt.302.1598347010745; Tue, 25 Aug 2020 02:16:50 -0700 (PDT) Received: from btopel-mobl.ger.intel.com ([192.55.55.45]) by smtp.gmail.com with ESMTPSA id 2sm2121857pjg.32.2020.08.25.02.16.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 25 Aug 2020 02:16:50 -0700 (PDT) From: =?utf-8?b?QmrDtnJuIFTDtnBlbA==?= To: jeffrey.t.kirsher@intel.com, intel-wired-lan@lists.osuosl.org Cc: =?utf-8?b?QmrDtnJuIFTDtnBlbA==?= , magnus.karlsson@intel.com, magnus.karlsson@gmail.com, netdev@vger.kernel.org, maciej.fijalkowski@intel.com, piotr.raczynski@intel.com, maciej.machnikowski@intel.com, lirongqing@baidu.com Subject: [PATCH net 1/3] i40e: avoid premature Rx buffer reuse Date: Tue, 25 Aug 2020 11:16:27 +0200 Message-Id: <20200825091629.12949-2-bjorn.topel@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200825091629.12949-1-bjorn.topel@gmail.com> References: <20200825091629.12949-1-bjorn.topel@gmail.com> MIME-Version: 1.0 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Björn Töpel The page recycle code, incorrectly, relied on that a page fragment could not be freed inside xdp_do_redirect(). This assumption leads to that page fragments that are used by the stack/XDP redirect can be reused and overwritten. To avoid this, store the page count prior invoking xdp_do_redirect(). Longer explanation: Intel NICs have a recycle mechanism. The main idea is that a page is split into two parts. One part is owned by the driver, one part might be owned by someone else, such as the stack. t0: Page is allocated, and put on the Rx ring +--------------- used by NIC ->| upper buffer (rx_buffer) +--------------- | lower buffer +--------------- page count == USHRT_MAX rx_buffer->pagecnt_bias == USHRT_MAX t1: Buffer is received, and passed to the stack (e.g.) +--------------- | upper buff (skb) +--------------- used by NIC ->| lower buffer (rx_buffer) +--------------- page count == USHRT_MAX rx_buffer->pagecnt_bias == USHRT_MAX - 1 t2: Buffer is received, and redirected +--------------- | upper buff (skb) +--------------- used by NIC ->| lower buffer (rx_buffer) +--------------- Now, prior calling xdp_do_redirect(): page count == USHRT_MAX rx_buffer->pagecnt_bias == USHRT_MAX - 2 This means that buffer *cannot* be flipped/reused, because the skb is still using it. The problem arises when xdp_do_redirect() actually frees the segment. Then we get: page count == USHRT_MAX - 1 rx_buffer->pagecnt_bias == USHRT_MAX - 2 From a recycle perspective, the buffer can be flipped and reused, which means that the skb data area is passed to the Rx HW ring! To work around this, the page count is stored prior calling xdp_do_redirect(). Note that this is not optimal, since the NIC could actually reuse the "lower buffer" again. However, then we need to track whether XDP_REDIRECT consumed the buffer or not. Fixes: d9314c474d4f ("i40e: add support for XDP_REDIRECT") Reported-by: Li RongQing Signed-off-by: Björn Töpel --- drivers/net/ethernet/intel/i40e/i40e_txrx.c | 28 +++++++++++++++------ 1 file changed, 21 insertions(+), 7 deletions(-) diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.c b/drivers/net/ethernet/intel/i40e/i40e_txrx.c index 3e5c566ceb01..5e446dc39190 100644 --- a/drivers/net/ethernet/intel/i40e/i40e_txrx.c +++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.c @@ -1873,7 +1873,8 @@ static inline bool i40e_page_is_reusable(struct page *page) * * In either case, if the page is reusable its refcount is increased. **/ -static bool i40e_can_reuse_rx_page(struct i40e_rx_buffer *rx_buffer) +static bool i40e_can_reuse_rx_page(struct i40e_rx_buffer *rx_buffer, + int rx_buffer_pgcnt) { unsigned int pagecnt_bias = rx_buffer->pagecnt_bias; struct page *page = rx_buffer->page; @@ -1884,7 +1885,7 @@ static bool i40e_can_reuse_rx_page(struct i40e_rx_buffer *rx_buffer) #if (PAGE_SIZE < 8192) /* if we are only owner of page we can reuse it */ - if (unlikely((page_count(page) - pagecnt_bias) > 1)) + if (unlikely((rx_buffer_pgcnt - pagecnt_bias) > 1)) return false; #else #define I40E_LAST_OFFSET \ @@ -1939,6 +1940,15 @@ static void i40e_add_rx_frag(struct i40e_ring *rx_ring, #endif } +static int i40e_rx_buffer_page_count(struct i40e_rx_buffer *rx_buffer) +{ +#if (PAGE_SIZE < 8192) + return page_count(rx_buffer->page); +#else + return 0; +#endif +} + /** * i40e_get_rx_buffer - Fetch Rx buffer and synchronize data for use * @rx_ring: rx descriptor ring to transact packets on @@ -1948,11 +1958,13 @@ static void i40e_add_rx_frag(struct i40e_ring *rx_ring, * for use by the CPU. */ static struct i40e_rx_buffer *i40e_get_rx_buffer(struct i40e_ring *rx_ring, - const unsigned int size) + const unsigned int size, + int *rx_buffer_pgcnt) { struct i40e_rx_buffer *rx_buffer; rx_buffer = i40e_rx_bi(rx_ring, rx_ring->next_to_clean); + *rx_buffer_pgcnt = i40e_rx_buffer_page_count(rx_buffer); prefetchw(rx_buffer->page); /* we are reusing so sync this buffer for CPU use */ @@ -2112,9 +2124,10 @@ static struct sk_buff *i40e_build_skb(struct i40e_ring *rx_ring, * either recycle the buffer or unmap it and free the associated resources. */ static void i40e_put_rx_buffer(struct i40e_ring *rx_ring, - struct i40e_rx_buffer *rx_buffer) + struct i40e_rx_buffer *rx_buffer, + int rx_buffer_pgcnt) { - if (i40e_can_reuse_rx_page(rx_buffer)) { + if (i40e_can_reuse_rx_page(rx_buffer, rx_buffer_pgcnt)) { /* hand second half of page back to the ring */ i40e_reuse_rx_page(rx_ring, rx_buffer); } else { @@ -2319,6 +2332,7 @@ static int i40e_clean_rx_irq(struct i40e_ring *rx_ring, int budget) unsigned int xdp_xmit = 0; bool failure = false; struct xdp_buff xdp; + int rx_buffer_pgcnt; #if (PAGE_SIZE < 8192) xdp.frame_sz = i40e_rx_frame_truesize(rx_ring, 0); @@ -2370,7 +2384,7 @@ static int i40e_clean_rx_irq(struct i40e_ring *rx_ring, int budget) break; i40e_trace(clean_rx_irq, rx_ring, rx_desc, skb); - rx_buffer = i40e_get_rx_buffer(rx_ring, size); + rx_buffer = i40e_get_rx_buffer(rx_ring, size, &rx_buffer_pgcnt); /* retrieve a buffer from the ring */ if (!skb) { @@ -2413,7 +2427,7 @@ static int i40e_clean_rx_irq(struct i40e_ring *rx_ring, int budget) break; } - i40e_put_rx_buffer(rx_ring, rx_buffer); + i40e_put_rx_buffer(rx_ring, rx_buffer, rx_buffer_pgcnt); cleaned_count++; if (i40e_is_non_eop(rx_ring, rx_desc, skb))