netdev - [PATCH net] virtio-net: fix overflow inside virtnet_rq

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Message-Id: <20240820071913.68004-1-xuanzhuo@linux.alibaba.com>
Date: Tue, 20 Aug 2024 15:19:13 +0800
From: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
To: netdev@...r.kernel.org
Cc: "Michael S. Tsirkin" <mst@...hat.com>,
	Jason Wang <jasowang@...hat.com>,
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
	Eugenio Pérez <eperezma@...hat.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	virtualization@...ts.linux.dev,
	"Si-Wei Liu" <si-wei.liu@...cle.com>,
	Darren Kenny <darren.kenny@...cle.com>
Subject: [PATCH net] virtio-net: fix overflow inside virtnet_rq_alloc

leads to regression on VM with the sysctl value of:

- net.core.high_order_alloc_disable=1

which could see reliable crashes or scp failure (scp a file 100M in size
to VM):

The issue is that the virtnet_rq_dma takes up 16 bytes at the beginning
of a new frag. When the frag size is larger than PAGE_SIZE,
everything is fine. However, if the frag is only one page and the
total size of the buffer and virtnet_rq_dma is larger than one page, an
overflow may occur. In this case, if an overflow is possible, I adjust
the buffer size. If net.core.high_order_alloc_disable=1, the maximum
buffer size is 4096 - 16. If net.core.high_order_alloc_disable=0, only
the first buffer of the frag is affected.

Fixes: f9dac92ba908 ("virtio_ring: enable premapped mode whatever use_dma_api")
Reported-by: "Si-Wei Liu" <si-wei.liu@...cle.com>
Closes: http://lore.kernel.org/all/8b20cc28-45a9-4643-8e87-ba164a540c0a@oracle.com
Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
---
 drivers/net/virtio_net.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index c6af18948092..e5286a6da863 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -918,9 +918,6 @@ static void *virtnet_rq_alloc(struct receive_queue *rq, u32 size, gfp_t gfp)
 	void *buf, *head;
 	dma_addr_t addr;
 
-	if (unlikely(!skb_page_frag_refill(size, alloc_frag, gfp)))
-		return NULL;
-
 	head = page_address(alloc_frag->page);
 
 	dma = head;
@@ -2421,6 +2418,9 @@ static int add_recvbuf_small(struct virtnet_info *vi, struct receive_queue *rq,
 	len = SKB_DATA_ALIGN(len) +
 	      SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
 
+	if (unlikely(!skb_page_frag_refill(len, &rq->alloc_frag, gfp)))
+		return -ENOMEM;
+
 	buf = virtnet_rq_alloc(rq, len, gfp);
 	if (unlikely(!buf))
 		return -ENOMEM;
@@ -2521,6 +2521,12 @@ static int add_recvbuf_mergeable(struct virtnet_info *vi,
 	 */
 	len = get_mergeable_buf_len(rq, &rq->mrg_avg_pkt_len, room);
 
+	if (unlikely(!skb_page_frag_refill(len + room, alloc_frag, gfp)))
+		return -ENOMEM;
+
+	if (!alloc_frag->offset && len + room + sizeof(struct virtnet_rq_dma) > alloc_frag->size)
+		len -= sizeof(struct virtnet_rq_dma);
+
 	buf = virtnet_rq_alloc(rq, len + room, gfp);
 	if (unlikely(!buf))
 		return -ENOMEM;
-- 
2.32.0.3.g01195cf9f