[PATCH] drivers: net: vmxnet3: fix possible NULL pointer dereference in vmxnet3_rq_cleanup()

[Zixuan Fu <r33s3n6@gmail.com>]

In vmxnet3_rq_create(), when dma_alloc_coherent() fails, 
vmxnet3_rq_destroy() is called. It sets rq->rx_ring[i].base to NULL. Then
vmxnet3_rq_create() returns an error to its callers mxnet3_rq_create_all()
-> vmxnet3_change_mtu(). Then vmxnet3_change_mtu() calls 
vmxnet3_force_close() -> dev_close() in error handling code. And the driver
calls vmxnet3_close() -> vmxnet3_quiesce_dev() -> vmxnet3_rq_cleanup_all()
-> vmxnet3_rq_cleanup(). In vmxnet3_rq_cleanup(), 
rq->rx_ring[ring_idx].base is accessed, but this variable is NULL, causing
a NULL pointer dereference.

To fix this possible bug, an if statement is added to check whether 
rq->rx_ring[ring_idx].base is NULL in vmxnet3_rq_cleanup().

The error log in our fault-injection testing is shown as follows:

[   65.220135] BUG: kernel NULL pointer dereference, address: 0000000000000008
...
[   65.222633] RIP: 0010:vmxnet3_rq_cleanup_all+0x396/0x4e0 [vmxnet3]
...
[   65.227977] Call Trace:
...
[   65.228262]  vmxnet3_quiesce_dev+0x80f/0x8a0 [vmxnet3]
[   65.228580]  vmxnet3_close+0x2c4/0x3f0 [vmxnet3]
[   65.228866]  __dev_close_many+0x288/0x350
[   65.229607]  dev_close_many+0xa4/0x480
[   65.231124]  dev_close+0x138/0x230
[   65.231933]  vmxnet3_force_close+0x1f0/0x240 [vmxnet3]
[   65.232248]  vmxnet3_change_mtu+0x75d/0x920 [vmxnet3]
...


Reported-by: TOTE Robot <oslab@tsinghua.edu.cn>
Signed-off-by: Zixuan Fu <r33s3n6@gmail.com>
---
 drivers/net/vmxnet3/vmxnet3_drv.c | 42 ++++++++++++++++---------------
 1 file changed, 22 insertions(+), 20 deletions(-)

diff --git a/drivers/net/vmxnet3/vmxnet3_drv.c b/drivers/net/vmxnet3/vmxnet3_drv.c
index d9d90baac72a..247fbdfe834a 100644
--- a/drivers/net/vmxnet3/vmxnet3_drv.c
+++ b/drivers/net/vmxnet3/vmxnet3_drv.c
@@ -1667,28 +1667,30 @@ vmxnet3_rq_cleanup(struct vmxnet3_rx_queue *rq,
 	struct Vmxnet3_RxDesc *rxd;
 
 	for (ring_idx = 0; ring_idx < 2; ring_idx++) {
-		for (i = 0; i < rq->rx_ring[ring_idx].size; i++) {
-#ifdef __BIG_ENDIAN_BITFIELD
-			struct Vmxnet3_RxDesc rxDesc;
-#endif
-			vmxnet3_getRxDesc(rxd,
-				&rq->rx_ring[ring_idx].base[i].rxd, &rxDesc);
-
-			if (rxd->btype == VMXNET3_RXD_BTYPE_HEAD &&
-					rq->buf_info[ring_idx][i].skb) {
-				dma_unmap_single(&adapter->pdev->dev, rxd->addr,
-						 rxd->len, DMA_FROM_DEVICE);
-				dev_kfree_skb(rq->buf_info[ring_idx][i].skb);
-				rq->buf_info[ring_idx][i].skb = NULL;
-			} else if (rxd->btype == VMXNET3_RXD_BTYPE_BODY &&
-					rq->buf_info[ring_idx][i].page) {
-				dma_unmap_page(&adapter->pdev->dev, rxd->addr,
-					       rxd->len, DMA_FROM_DEVICE);
-				put_page(rq->buf_info[ring_idx][i].page);
-				rq->buf_info[ring_idx][i].page = NULL;
+		if (rq->rx_ring[ring_idx].base) {
+			for (i = 0; i < rq->rx_ring[ring_idx].size; i++) {
+	#ifdef __BIG_ENDIAN_BITFIELD
+				struct Vmxnet3_RxDesc rxDesc;
+	#endif
+				vmxnet3_getRxDesc(rxd,
+					&rq->rx_ring[ring_idx].base[i].rxd, &rxDesc);
+
+				if (rxd->btype == VMXNET3_RXD_BTYPE_HEAD &&
+						rq->buf_info[ring_idx][i].skb) {
+					dma_unmap_single(&adapter->pdev->dev, rxd->addr,
+							 rxd->len, DMA_FROM_DEVICE);
+					dev_kfree_skb(rq->buf_info[ring_idx][i].skb);
+					rq->buf_info[ring_idx][i].skb = NULL;
+				} else if (rxd->btype == VMXNET3_RXD_BTYPE_BODY &&
+						rq->buf_info[ring_idx][i].page) {
+					dma_unmap_page(&adapter->pdev->dev, rxd->addr,
+						       rxd->len, DMA_FROM_DEVICE);
+					put_page(rq->buf_info[ring_idx][i].page);
+					rq->buf_info[ring_idx][i].page = NULL;
+				}
 			}
 		}
-
+
 		rq->rx_ring[ring_idx].gen = VMXNET3_INIT_GEN;
 		rq->rx_ring[ring_idx].next2fill =
 					rq->rx_ring[ring_idx].next2comp = 0;
-- 
2.25.1