net: vmxnet3: fix possible use-after-free bugs in vmxnet3_rq_alloc_rx_buf()

net: vmxnet3: fix possible use-after-free bugs in vmxnet3_rq_alloc_rx_buf()

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 be cleared after
they are freed.

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
...

Fixes: a794ea5dfda58 ("vmxnet3: fix checks for dma mapping errors")
Reported-by: TOTE Robot <oslab@tsinghua.edu.cn>
Signed-off-by: Zixuan Fu <r33s3n6@gmail.com>
Link: https://lore.kernel.org/r/20220514050656.2636588-1-r33s3n6@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>