linux-kernel - Re: [BUG] KASAN: slab-use-after-free Read in xhci_hub

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Message-ID: <8033fcb7-e97d-4b6d-a3fb-a9a49f8b69f2@rowland.harvard.edu>
Date: Thu, 17 Jul 2025 22:05:16 -0400
From: Alan Stern <stern@...land.harvard.edu>
To: cen zhang <zzzccc427@...il.com>
Cc: mathias.nyman@...el.com, gregkh@...uxfoundation.org,
	linux-kernel@...r.kernel.org, baijiaju1990@...il.com,
	zhenghaoran154@...il.com, r33s3n6@...il.com,
	linux-usb@...r.kernel.org, gality365@...il.com
Subject: Re: [BUG] KASAN: slab-use-after-free Read in xhci_hub_control

On Thu, Jul 17, 2025 at 08:24:17PM +0800, cen zhang wrote:
> Hi maintainers,
> 
> I've encountered a kernel crash in the xhci driver, which was found by
> Syzkaller on kernel version 6.16.0-rc6 (commit 155a3c003e55).
> 
> The KASAN report points to a slab-use-after-free read within
> xhci_hub_control. What we find puzzling is that the free operation
> occurred in a completely different module, as indicated by the free
> stack trace.
> 
> We suspect this might not be a false positive, but rather a complex
> bug whose root cause is not a simple UAF within the same driver. We've
> tried to trace how this could happen but are struggling to understand
> the connection.
> 
> Could you possibly offer your expertise and help us understand if this
> is a known issue or a new bug? Any insight you could provide would be
> immensely helpful.

My initial guess is that you're experiencing pointer corruption.  Such
bugs are notoriously difficult to locate and pin down.

Alan Stern