linux-kernel - Re: [PATCH] [PATCH net v2]vexy: Fix a use-after-free bug in vxge-main.c

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Date:   Wed, 15 Jun 2022 19:50:50 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Wentao_Liang <Wentao_Liang_g@....com>, jdmason@...zu.us
Cc:     davem@...emloft.net, edumazet@...gle.com, pabeni@...hat.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [PATCH net v2]vexy: Fix a use-after-free bug in
 vxge-main.c

Jon, if you're there, do you have any sense on whether this HW is still
in production somewhere? I scrolled thru last 5 years of the git history
and there doesn't seem to be any meaningful change here while there's a
significant volume of refactoring going in. 

On the patch itself:

On Wed, 15 Jun 2022 09:38:16 +0800 Wentao_Liang wrote:
> Subject: [PATCH] [PATCH net v2]vexy: Fix a use-after-free bug in vxge-main.c

No need to repeat "[PATCH]"
The driver is not called "vexy" as far as I can tell.

> 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.

Are you sure the bar0 is not needed by the netdev? You're freeing
memory that the netdev may need until it's unregistered.