From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Martin Habets <habetsm.xilinx@gmail.com>,
        Jiasheng Jiang <jiasheng@iscas.ac.cn>,
        Jakub Kicinski <kuba@kernel.org>
Subject: [PATCH 5.15 15/72] sfc: The RX page_ring is optional
Date:   Mon, 10 Jan 2022 08:22:52 +0100
Message-Id: <20220110071822.069210729@linuxfoundation.org>
In-Reply-To: <20220110071821.500480371@linuxfoundation.org>
References: <20220110071821.500480371@linuxfoundation.org>
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From: Martin Habets <habetsm.xilinx@gmail.com>

commit 1d5a474240407c38ca8c7484a656ee39f585399c upstream.

The RX page_ring is an optional feature that improves
performance. When allocation fails the driver can still
function, but possibly with a lower bandwidth.
Guard against dereferencing a NULL page_ring.

Fixes: 2768935a4660 ("sfc: reuse pages to avoid DMA mapping/unmapping costs")
Signed-off-by: Martin Habets <habetsm.xilinx@gmail.com>
Reported-by: Jiasheng Jiang <jiasheng@iscas.ac.cn>
Link: https://lore.kernel.org/r/164111288276.5798.10330502993729113868.stgit@palantir17.mph.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/ethernet/sfc/falcon/rx.c |    5 +++++
 drivers/net/ethernet/sfc/rx_common.c |    5 +++++
 2 files changed, 10 insertions(+)

--- a/drivers/net/ethernet/sfc/falcon/rx.c
+++ b/drivers/net/ethernet/sfc/falcon/rx.c
@@ -110,6 +110,8 @@ static struct page *ef4_reuse_page(struc
 	struct ef4_rx_page_state *state;
 	unsigned index;
 
+	if (unlikely(!rx_queue->page_ring))
+		return NULL;
 	index = rx_queue->page_remove & rx_queue->page_ptr_mask;
 	page = rx_queue->page_ring[index];
 	if (page == NULL)
@@ -293,6 +295,9 @@ static void ef4_recycle_rx_pages(struct
 {
 	struct ef4_rx_queue *rx_queue = ef4_channel_get_rx_queue(channel);
 
+	if (unlikely(!rx_queue->page_ring))
+		return;
+
 	do {
 		ef4_recycle_rx_page(channel, rx_buf);
 		rx_buf = ef4_rx_buf_next(rx_queue, rx_buf);
--- a/drivers/net/ethernet/sfc/rx_common.c
+++ b/drivers/net/ethernet/sfc/rx_common.c
@@ -45,6 +45,8 @@ static struct page *efx_reuse_page(struc
 	unsigned int index;
 	struct page *page;
 
+	if (unlikely(!rx_queue->page_ring))
+		return NULL;
 	index = rx_queue->page_remove & rx_queue->page_ptr_mask;
 	page = rx_queue->page_ring[index];
 	if (page == NULL)
@@ -114,6 +116,9 @@ void efx_recycle_rx_pages(struct efx_cha
 {
 	struct efx_rx_queue *rx_queue = efx_channel_get_rx_queue(channel);
 
+	if (unlikely(!rx_queue->page_ring))
+		return;
+
 	do {
 		efx_recycle_rx_page(channel, rx_buf);
 		rx_buf = efx_rx_buf_next(rx_queue, rx_buf);