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SubjectRe: [PATCH] Fix a use-after-free bug
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On Tue, 2022-06-14 at 09:28 +0800, Wentao_Liang wrote:
> 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.
>
> /***********************report begin***************************/
>
> 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
> ...
> [ 182.070606]
> ==================================================================
> [ 182.071374] Disabling lock debugging due to kernel taint
>
> /************************report end***************************/

It's better to include a complete backtrace

>
> 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.
>
> /************************report begin*************************/
>
> root@kernel:~# echo 1 > /sys/bus/pci/devices/0000:00:03.0/remove
> root@kernel:~#
>
> /************************report end***************************/
>
> Signed-off-by: Wentao_Liang <Wentao_Liang_g@163.com>

Please include a 'Fixes' tag pointing to the commit introducing the
bug, and please specify the relevant target tree and driver in the
patch subj. It should be something alike:

[PATCH net v2] vxge: fix a use-after-free bug

Thanks,

Paolo

> ---
> drivers/net/ethernet/neterion/vxge/vxge-main.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/neterion/vxge/vxge-main.c b/drivers/net/ethernet/neterion/vxge/vxge-main.c
> index fa5d4ddf429b..092fd0ae5831 100644
> --- a/drivers/net/ethernet/neterion/vxge/vxge-main.c
> +++ b/drivers/net/ethernet/neterion/vxge/vxge-main.c
> @@ -4736,10 +4736,10 @@ static void vxge_remove(struct pci_dev *pdev)
> for (i = 0; i < vdev->no_of_vpath; i++)
> vxge_free_mac_add_list(&vdev->vpaths[i]);
>
> + iounmap(vdev->bar0);
> vxge_device_unregister(hldev);
> /* Do not call pci_disable_sriov here, as it will break child devices */
> vxge_hw_device_terminate(hldev);
> - iounmap(vdev->bar0);
> pci_release_region(pdev, 0);
> pci_disable_device(pdev);
> driver_config->config_dev_cnt--;

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