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

From: Jakub Kicinski <[email-masked]>
Date: Mon, 9 May 2022 16:01:57 -0700

On Fri,  6 May 2022 21:37:48 +0800 Zixuan Fu wrote:
> 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_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 <[email-masked]>
> Signed-off-by: Zixuan Fu <[email-masked]>
> ---
>  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;

If destroy_all got called presumably we can just check ring 0 is NULL
and exit early rather than skipping ring by ring?

Either way, please rewrite the change so you don't have to re-indent
the entire block.

>  	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;
> +				}
>  			}
>  		}
> -
> +

What's this change?

>  		rq->rx_ring[ring_idx].gen = VMXNET3_INIT_GEN;
>  		rq->rx_ring[ring_idx].next2fill =
>  					rq->rx_ring[ring_idx].next2comp = 0;