[dpdk-dev] [PATCH v2] kni: fix possible kernel crash with va2pa

[Yangchao Zhou <zhouyates@gmail.com>]

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().

Signed-off-by: Yangchao Zhou <zhouyates@gmail.com>
---
v2: Add an explanation that causes this problem.
    Use m->next to store physical address.
---
 kernel/linux/kni/kni_net.c                    | 42 +++++++++++--------
 .../eal/include/exec-env/rte_kni_common.h     |  2 +-
 lib/librte_kni/rte_kni.c                      | 15 ++++++-
 3 files changed, 40 insertions(+), 19 deletions(-)

diff --git a/kernel/linux/kni/kni_net.c b/kernel/linux/kni/kni_net.c
index 7371b6d58..106b5153f 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, *_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;
+
+				_kva = kva;
+				kva = pa2kva(kva->next);
+				/* Convert physical address to virtual address */
+				_kva->next = pa2va(_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, *_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));
+				_kva = kva;
+				kva = pa2kva(kva->next);
 				data_kva = kva2data_kva(kva);
+				/* Convert physical address to virtual address */
+				_kva->next = pa2va(_kva->next, kva);
 			}
 		}
 
@@ -481,7 +486,7 @@ 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, *_kva;
 	void *data_kva;
 	struct sk_buff *skb;
 	struct net_device *dev = kni->net_dev;
@@ -545,8 +550,11 @@ kni_net_rx_lo_fifo_skb(struct kni_dev *kni)
 				if (!kva->next)
 					break;
 
-				kva = pa2kva(va2pa(kva->next, kva));
+				_kva = kva;
+				kva = pa2kva(kva->next);
 				data_kva = kva2data_kva(kva);
+				/* Convert physical address to virtual address */
+				_kva->next = pa2va(_kva->next, kva);
 			}
 		}
 
diff --git a/lib/librte_eal/linuxapp/eal/include/exec-env/rte_kni_common.h b/lib/librte_eal/linuxapp/eal/include/exec-env/rte_kni_common.h
index 5afa08713..688db9758 100644
--- a/lib/librte_eal/linuxapp/eal/include/exec-env/rte_kni_common.h
+++ b/lib/librte_eal/linuxapp/eal/include/exec-env/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 73aeccccf..74b1ff5b6 100644
--- a/lib/librte_kni/rte_kni.c
+++ b/lib/librte_kni/rte_kni.c
@@ -353,6 +353,19 @@ 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)
@@ -550,7 +563,7 @@ rte_kni_tx_burst(struct rte_kni *kni, struct rte_mbuf **mbufs, unsigned num)
 	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);
 
-- 
2.19.1.windows.1