The pointer vdev points to a memory region adjacent to a net_device
structure ndev, which is a field of hldev. At line 4740, the invocation
to vxge_device_unregister unregisters device hldev, and it also releases
the memory region pointed by vdev->bar0. At line 4743, the freed memory
region is referenced (i.e., iounmap(vdev->bar0)), resulting in a
use-after-free vulnerability. We can fix the bug by calling iounmap
before vxge_device_unregister.

4721.      static void vxge_remove(struct pci_dev *pdev)
4722.      {
4723.             struct __vxge_hw_device *hldev;
4724.             struct vxgedev *vdev;
…
4731.             vdev = netdev_priv(hldev->ndev);
…
4740.             vxge_device_unregister(hldev);
4741.             /* Do not call pci_disable_sriov here, as it
						will break child devices */
4742.             vxge_hw_device_terminate(hldev);
4743.             iounmap(vdev->bar0);
…
4749              vxge_debug_init(vdev->level_trace, "%s:%d
								Device unregistered",
4750                            __func__, __LINE__);
4751              vxge_debug_entryexit(vdev->level_trace, "%s:%d
								Exiting...", __func__,
4752                          __LINE__);
4753.      }

This is the screenshot when the vulnerability is triggered by using
KASAN. We can see that there is a use-after-free reported by KASAN.

/***************************start**************************/

root@kernel:~# echo 1 > /sys/bus/pci/devices/0000:00:03.0/remove
[  178.296316] vxge_remove
[  182.057081]
 ==================================================================
[  182.057548] BUG: KASAN: use-after-free in vxge_remove+0xe0/0x15c
[  182.057760] Read of size 8 at addr ffff888006c76598 by task bash/119
[  182.057983]
[  182.058747] CPU: 0 PID: 119 Comm: bash Not tainted 5.18.0 #5
[  182.058919] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS
rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
[  182.059463] Call Trace:
[  182.059726]  <TASK>
[  182.060017]  dump_stack_lvl+0x34/0x44
[  182.060316]  print_report.cold+0xb2/0x6b7
[  182.060401]  ? kfree+0x89/0x290
[  182.060478]  ? vxge_remove+0xe0/0x15c
[  182.060545]  kasan_report+0xa9/0x120
[  182.060629]  ? vxge_remove+0xe0/0x15c
[  182.060706]  vxge_remove+0xe0/0x15c
[  182.060793]  pci_device_remove+0x5d/0xe0
[  182.060968]  device_release_driver_internal+0xf1/0x180
[  182.061063]  pci_stop_bus_device+0xae/0xe0
[  182.061150]  pci_stop_and_remove_bus_device_locked+0x11/0x20
[  182.061236]  remove_store+0xc6/0xe0
[  182.061297]  ? subordinate_bus_number_show+0xc0/0xc0
[  182.061359]  ? __mutex_lock_slowpath+0x10/0x10
[  182.061438]  ? sysfs_kf_write+0x6d/0xa0
[  182.061525]  kernfs_fop_write_iter+0x1b0/0x260
[  182.061610]  ? sysfs_kf_bin_read+0xf0/0xf0
[  182.061695]  new_sync_write+0x209/0x310
[  182.061789]  ? new_sync_read+0x310/0x310
[  182.061865]  ? cgroup_rstat_updated+0x5c/0x170
[  182.061937]  ? preempt_count_sub+0xf/0xb0
[  182.061995]  ? pick_next_entity+0x13a/0x220
[  182.062063]  ? __inode_security_revalidate+0x44/0x80
[  182.062155]  ? security_file_permission+0x46/0x2a0
[  182.062230]  vfs_write+0x33f/0x3e0
[  182.062303]  ksys_write+0xb4/0x150
[  182.062369]  ? __ia32_sys_read+0x40/0x40
[  182.062451]  do_syscall_64+0x3b/0x90
[  182.062531]  entry_SYSCALL_64_after_hwframe+0x46/0xb0
[  182.062894] RIP: 0033:0x7f3f37d17274
[  182.063558] Code: 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b3 0f 1f
80 00 00 00 00 48 8d 05 89 54 0d 00 8b 00 85 c0 75 13 b8 01 00 00 00 0f
05 <48> 3d 00 f0 ff ff 77 54 c3 0f 1f 00 41 54 49 89 d4 55 48 89 f5 53
[  182.063797] RSP: 002b:00007ffd5ba9e178 EFLAGS: 00000246
ORIG_RAX: 0000000000000001
[  182.064117] RAX: ffffffffffffffda RBX: 0000000000000002
RCX: 00007f3f37d17274
[  182.064219] RDX: 0000000000000002 RSI: 000055bbec327180
RDI: 0000000000000001
[  182.064315] RBP: 000055bbec327180 R08: 000000000000000a
R09: 00007f3f37de7cf0
[  182.064414] R10: 000000000000000a R11: 0000000000000246
R12: 00007f3f37de8760
[  182.064513] R13: 0000000000000002 R14: 00007f3f37de3760
R15: 0000000000000002
[  182.064691]  </TASK>
[  182.064916]
[  182.065224] The buggy address belongs to the physical page:
[  182.065804] page:00000000ef31e4f4 refcount:0 mapcount:0
mapping:0000000000000000 index:0x0 pfn:0x6c76
[  182.067419] flags: 0x100000000000000(node=0|zone=1)
[  182.068997] raw: 0100000000000000 0000000000000000
ffffea00001b1d88 0000000000000000
[  182.069118] raw: 0000000000000000 0000000000000000
00000000ffffffff 0000000000000000
[  182.069294] page dumped because: kasan: bad access detected
[  182.069331]
[  182.069360] Memory state around the buggy address:
[  182.070006]  ffff888006c76480: ff ff ff ff ff ff ff ff ff ff ff
 ff ff ff ff ff
[  182.070136]  ffff888006c76500: ff ff ff ff ff ff ff ff ff ff ff
 ff ff ff ff ff
[  182.070230] >ffff888006c76580: ff ff ff ff ff ff ff ff ff ff ff
 ff ff ff ff ff
[  182.070305]                             ^
[  182.070456]  ffff888006c76600: ff ff ff ff ff ff ff ff ff ff ff
 ff ff ff ff ff
[  182.070505]  ffff888006c76680: ff ff ff ff ff ff ff ff ff ff ff
 ff ff ff ff ff
[  182.070606]
==================================================================
[  182.071374] Disabling lock debugging due to kernel taint

/*****************************end*****************************/

After fixing the bug as done in the patch, we can find KASAN do not report
 the bug and the device(00:03.0) has been successfully removed.

/*****************************start***************************/

root@kernel:~# echo 1 > /sys/bus/pci/devices/0000:00:03.0/remove
root@kernel:~#

/******************************end****************************/
Signed-off-by: Wentao_Liang <Wentao_Liang_g@163.com>
Signed-off-by: David S. Miller <davem@davemloft.net>