Subject: Re: [PATCH] driver: net: vmxnet3: fix possible use-after-free bugs in vmxnet3_rq_alloc_rx_buf()

From: Jakub Kicinski <[email-masked]>
Date: Mon, 9 May 2022 16:05:02 -0700

On Fri,  6 May 2022 20:31:18 +0800 Zixuan Fu wrote:
> In vmxnet3_rq_alloc_rx_buf(), when dma_map_single() fails, rbi->skb is
> freed immediately. Similarly, in another branch, when dma_map_page() fails,
> rbi->page is also freed. In the two cases, vmxnet3_rq_alloc_rx_buf()
> returns an error to its callers vmxnet3_rq_init() -> vmxnet3_rq_init_all()
> -> vmxnet3_activate_dev(). Then vmxnet3_activate_dev() calls  
> vmxnet3_rq_cleanup_all() in error handling code, and rbi->skb or rbi->page
> are freed again in vmxnet3_rq_cleanup_all(), causing use-after-free bugs.
> 
> To fix these possible bugs, rbi->skb and rbi->page should not be freed in 
> mxnet3_rq_alloc_rx_buf() when dma_map_single() fails.

You should not leave unmapped data on the ring. Freeing is fine, just
make sure the pointer is cleared.

> The error log in our fault-injection testing is shown as follows:
> 
> [   14.319016] BUG: KASAN: use-after-free in consume_skb+0x2f/0x150
> ...
> [   14.321586] Call Trace:
> ...
> [   14.325357]  consume_skb+0x2f/0x150
> [   14.325671]  vmxnet3_rq_cleanup_all+0x33a/0x4e0 [vmxnet3]
> [   14.326150]  vmxnet3_activate_dev+0xb9d/0x2ca0 [vmxnet3]
> [   14.326616]  vmxnet3_open+0x387/0x470 [vmxnet3]
> ...
> [   14.361675] Allocated by task 351:
> ...
> [   14.362688]  __netdev_alloc_skb+0x1b3/0x6f0
> [   14.362960]  vmxnet3_rq_alloc_rx_buf+0x1b0/0x8d0 [vmxnet3]
> [   14.363317]  vmxnet3_activate_dev+0x3e3/0x2ca0 [vmxnet3]
> [   14.363661]  vmxnet3_open+0x387/0x470 [vmxnet3]
> ...
> [   14.367309] 
> [   14.367412] Freed by task 351:
> ...
> [   14.368932]  __dev_kfree_skb_any+0xd2/0xe0
> [   14.369193]  vmxnet3_rq_alloc_rx_buf+0x71e/0x8d0 [vmxnet3]
> [   14.369544]  vmxnet3_activate_dev+0x3e3/0x2ca0 [vmxnet3]
> [   14.369883]  vmxnet3_open+0x387/0x470 [vmxnet3]
> [   14.370174]  __dev_open+0x28a/0x420
> [   14.370399]  __dev_change_flags+0x192/0x590
> [   14.370667]  dev_change_flags+0x7a/0x180
> [   14.370919]  do_setlink+0xb28/0x3570
> [   14.371150]  rtnl_newlink+0x1160/0x1740
> [   14.371399]  rtnetlink_rcv_msg+0x5bf/0xa50
> [   14.371661]  netlink_rcv_skb+0x1cd/0x3e0
> [   14.371913]  netlink_unicast+0x5dc/0x840
> [   14.372169]  netlink_sendmsg+0x856/0xc40
> [   14.372420]  ____sys_sendmsg+0x8a7/0x8d0
> [   14.372673]  __sys_sendmsg+0x1c2/0x270
> [   14.372914]  do_syscall_64+0x41/0x90
> [   14.373145]  entry_SYSCALL_64_after_hwframe+0x44/0xae
> ...
> 
> Reported-by: TOTE Robot <[email-masked]>
> Signed-off-by: Zixuan Fu <[email-masked]>
> ---
>  drivers/net/vmxnet3/vmxnet3_drv.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/drivers/net/vmxnet3/vmxnet3_drv.c b/drivers/net/vmxnet3/vmxnet3_drv.c
> index d9d90baac72a..f17e9871ba27 100644
> --- a/drivers/net/vmxnet3/vmxnet3_drv.c
> +++ b/drivers/net/vmxnet3/vmxnet3_drv.c
> @@ -588,7 +588,6 @@ vmxnet3_rq_alloc_rx_buf(struct vmxnet3_rx_queue *rq, u32 ring_idx,
>  						DMA_FROM_DEVICE);
>  				if (dma_mapping_error(&adapter->pdev->dev,
>  						      rbi->dma_addr)) {
> -					dev_kfree_skb_any(rbi->skb);
>  					rq->stats.rx_buf_alloc_failure++;
>  					break;
>  				}
> @@ -612,7 +611,6 @@ vmxnet3_rq_alloc_rx_buf(struct vmxnet3_rx_queue *rq, u32 ring_idx,
>  						DMA_FROM_DEVICE);
>  				if (dma_mapping_error(&adapter->pdev->dev,
>  						      rbi->dma_addr)) {
> -					put_page(rbi->page);
>  					rq->stats.rx_buf_alloc_failure++;
>  					break;
>  				}