[dpdk-dev] [PATCH v3] kni: fix possible kernel crash with va2pa

[Yangchao Zhou]

va2pa depends on the physical address and virtual address offset of
current mbuf. It may get the wrong physical address of next mbuf which
allocated in another hugepage segment.

In rte_mempool_populate_default(), trying to allocate whole block of
contiguous memory could be failed. Then, it would reserve memory in
several memzones that have different physical address and virtual address
offsets. The rte_mempool_populate_default() is used by
rte_pktmbuf_pool_create().

Fixes: 8451269e6d7b ("kni: remove continuous memory restriction")

Signed-off-by: Yangchao Zhou <zhouyates at gmail.com>
---
 .../prog_guide/kernel_nic_interface.rst       |  6 ++-
 kernel/linux/kni/kni_net.c                    | 51 ++++++++++++-------
 .../linux/eal/include/rte_kni_common.h        |  2 +-
 lib/librte_kni/rte_kni.c                      | 16 +++++-
 lib/librte_kni/rte_kni_fifo.h                 | 12 +++++
 5 files changed, 65 insertions(+), 22 deletions(-)

diff --git a/doc/guides/prog_guide/kernel_nic_interface.rst b/doc/guides/prog_guide/kernel_nic_interface.rst
index daf87f4a8..2fd3b7983 100644
--- a/doc/guides/prog_guide/kernel_nic_interface.rst
+++ b/doc/guides/prog_guide/kernel_nic_interface.rst
@@ -268,12 +268,14 @@ Use Case: Ingress
 -----------------
 
 On the DPDK RX side, the mbuf is allocated by the PMD in the RX thread context.
-This thread will enqueue the mbuf in the rx_q FIFO.
+This thread will enqueue the mbuf in the rx_q FIFO, and the next pointers in mbuf-chain will convert to physical address.
 The KNI thread will poll all KNI active devices for the rx_q.
 If an mbuf is dequeued, it will be converted to a sk_buff and sent to the net stack via netif_rx().
-The dequeued mbuf must be freed, so the same pointer is sent back in the free_q FIFO.
+The dequeued mbuf must be freed, so the same pointer is sent back in the free_q FIFO,
+and next pointers must convert back to virtual address if exists before put in the free_q FIFO.
 
 The RX thread, in the same main loop, polls this FIFO and frees the mbuf after dequeuing it.
+The address conversion of the next pointer is to prevent the chained mbuf in different hugepage segments from causing kernel crash.
 
 Use Case: Egress
 ----------------
diff --git a/kernel/linux/kni/kni_net.c b/kernel/linux/kni/kni_net.c
index ad8365877..f65233aaa 100644
--- a/kernel/linux/kni/kni_net.c
+++ b/kernel/linux/kni/kni_net.c
@@ -61,18 +61,6 @@ kva2data_kva(struct rte_kni_mbuf *m)
 	return phys_to_virt(m->buf_physaddr + m->data_off);
 }
 
-/* virtual address to physical address */
-static void *
-va2pa(void *va, struct rte_kni_mbuf *m)
-{
-	void *pa;
-
-	pa = (void *)((unsigned long)va -
-			((unsigned long)m->buf_addr -
-			 (unsigned long)m->buf_physaddr));
-	return pa;
-}
-
 /*
  * It can be called to process the request.
  */
@@ -173,7 +161,10 @@ kni_fifo_trans_pa2va(struct kni_dev *kni,
 	struct rte_kni_fifo *src_pa, struct rte_kni_fifo *dst_va)
 {
 	uint32_t ret, i, num_dst, num_rx;
-	void *kva;
+	struct rte_kni_mbuf *kva, *prev_kva;
+	int nb_segs;
+	int kva_nb_segs;
+
 	do {
 		num_dst = kni_fifo_free_count(dst_va);
 		if (num_dst == 0)
@@ -188,6 +179,17 @@ kni_fifo_trans_pa2va(struct kni_dev *kni,
 		for (i = 0; i < num_rx; i++) {
 			kva = pa2kva(kni->pa[i]);
 			kni->va[i] = pa2va(kni->pa[i], kva);
+
+			kva_nb_segs = kva->nb_segs;
+			for (nb_segs = 0; nb_segs < kva_nb_segs; nb_segs++) {
+				if (!kva->next)
+					break;
+
+				prev_kva = kva;
+				kva = pa2kva(kva->next);
+				/* Convert physical address to virtual address */
+				prev_kva->next = pa2va(prev_kva->next, kva);
+			}
 		}
 
 		ret = kni_fifo_put(dst_va, kni->va, num_rx);
@@ -313,7 +315,7 @@ kni_net_rx_normal(struct kni_dev *kni)
 	uint32_t ret;
 	uint32_t len;
 	uint32_t i, num_rx, num_fq;
-	struct rte_kni_mbuf *kva;
+	struct rte_kni_mbuf *kva, *prev_kva;
 	void *data_kva;
 	struct sk_buff *skb;
 	struct net_device *dev = kni->net_dev;
@@ -363,8 +365,11 @@ kni_net_rx_normal(struct kni_dev *kni)
 				if (!kva->next)
 					break;
 
-				kva = pa2kva(va2pa(kva->next, kva));
+				prev_kva = kva;
+				kva = pa2kva(kva->next);
 				data_kva = kva2data_kva(kva);
+				/* Convert physical address to virtual address */
+				prev_kva->next = pa2va(prev_kva->next, kva);
 			}
 		}
 
@@ -396,7 +401,7 @@ kni_net_rx_lo_fifo(struct kni_dev *kni)
 	uint32_t ret;
 	uint32_t len;
 	uint32_t i, num, num_rq, num_tq, num_aq, num_fq;
-	struct rte_kni_mbuf *kva;
+	struct rte_kni_mbuf *kva, *next_kva;
 	void *data_kva;
 	struct rte_kni_mbuf *alloc_kva;
 	void *alloc_data_kva;
@@ -439,6 +444,13 @@ kni_net_rx_lo_fifo(struct kni_dev *kni)
 			data_kva = kva2data_kva(kva);
 			kni->va[i] = pa2va(kni->pa[i], kva);
 
+			while (kva->next) {
+				next_kva = pa2kva(kva->next);
+				/* Convert physical address to virtual address */
+				kva->next = pa2va(kva->next, next_kva);
+				kva = next_kva;
+			}
+
 			alloc_kva = pa2kva(kni->alloc_pa[i]);
 			alloc_data_kva = kva2data_kva(alloc_kva);
 			kni->alloc_va[i] = pa2va(kni->alloc_pa[i], alloc_kva);
@@ -481,7 +493,7 @@ kni_net_rx_lo_fifo_skb(struct kni_dev *kni)
 	uint32_t ret;
 	uint32_t len;
 	uint32_t i, num_rq, num_fq, num;
-	struct rte_kni_mbuf *kva;
+	struct rte_kni_mbuf *kva, *prev_kva;
 	void *data_kva;
 	struct sk_buff *skb;
 	struct net_device *dev = kni->net_dev;
@@ -545,8 +557,11 @@ kni_net_rx_lo_fifo_skb(struct kni_dev *kni)
 				if (!kva->next)
 					break;
 
-				kva = pa2kva(va2pa(kva->next, kva));
+				prev_kva = kva;
+				kva = pa2kva(kva->next);
 				data_kva = kva2data_kva(kva);
+				/* Convert physical address to virtual address */
+				prev_kva->next = pa2va(prev_kva->next, kva);
 			}
 		}
 
diff --git a/lib/librte_eal/linux/eal/include/rte_kni_common.h b/lib/librte_eal/linux/eal/include/rte_kni_common.h
index 91a1c1408..37d9ee8f0 100644
--- a/lib/librte_eal/linux/eal/include/rte_kni_common.h
+++ b/lib/librte_eal/linux/eal/include/rte_kni_common.h
@@ -86,7 +86,7 @@ struct rte_kni_mbuf {
 	/* fields on second cache line */
 	char pad3[8] __attribute__((__aligned__(RTE_CACHE_LINE_MIN_SIZE)));
 	void *pool;
-	void *next;
+	void *next;             /**< Physical address of next mbuf in kernel. */
 };
 
 /*
diff --git a/lib/librte_kni/rte_kni.c b/lib/librte_kni/rte_kni.c
index e29d0cc7d..6fc36f744 100644
--- a/lib/librte_kni/rte_kni.c
+++ b/lib/librte_kni/rte_kni.c
@@ -344,6 +344,19 @@ va2pa(struct rte_mbuf *m)
 			 (unsigned long)m->buf_iova));
 }
 
+static void *
+va2pa_all(struct rte_mbuf *mbuf)
+{
+	void *phy_mbuf = va2pa(mbuf);
+	struct rte_mbuf *next = mbuf->next;
+	while (next) {
+		mbuf->next = va2pa(next);
+		mbuf = next;
+		next = mbuf->next;
+	}
+	return phy_mbuf;
+}
+
 static void
 obj_free(struct rte_mempool *mp __rte_unused, void *opaque, void *obj,
 		unsigned obj_idx __rte_unused)
@@ -536,12 +549,13 @@ rte_kni_handle_request(struct rte_kni *kni)
 unsigned
 rte_kni_tx_burst(struct rte_kni *kni, struct rte_mbuf **mbufs, unsigned num)
 {
+	num = RTE_MIN(kni_fifo_free_count(kni->rx_q), num);
 	void *phy_mbufs[num];
 	unsigned int ret;
 	unsigned int i;
 
 	for (i = 0; i < num; i++)
-		phy_mbufs[i] = va2pa(mbufs[i]);
+		phy_mbufs[i] = va2pa_all(mbufs[i]);
 
 	ret = kni_fifo_put(kni->rx_q, phy_mbufs, num);
 
diff --git a/lib/librte_kni/rte_kni_fifo.h b/lib/librte_kni/rte_kni_fifo.h
index 287d7deb2..11d7fd6bd 100644
--- a/lib/librte_kni/rte_kni_fifo.h
+++ b/lib/librte_kni/rte_kni_fifo.h
@@ -104,3 +104,15 @@ kni_fifo_count(struct rte_kni_fifo *fifo)
 	unsigned fifo_read = __KNI_LOAD_ACQUIRE(&fifo->read);
 	return (fifo->len + fifo_write - fifo_read) & (fifo->len - 1);
 }
+
+/**
+ * Get the num of available elements in the fifo
+ */
+static inline uint32_t
+kni_fifo_free_count(struct rte_kni_fifo *fifo)
+{
+	uint32_t fifo_write = __KNI_LOAD_ACQUIRE(&fifo->write);
+	uint32_t fifo_read = __KNI_LOAD_ACQUIRE(&fifo->read);
+	return (fifo_read - fifo_write - 1) & (fifo->len - 1);
+}
+
-- 
2.17.1