linux-kernel - Re: [PATCH] ALSA: usb-audio: Fix NULL pointer deference in try_to_register

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Message-ID: <2025101453-backboned-shine-17b8@gregkh>
Date: Tue, 14 Oct 2025 07:26:41 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: Jiaming Zhang <r772577952@...il.com>
Cc: broonie@...nel.org, cryolitia@...ontech.com,
	linux-kernel@...r.kernel.org, linux-sound@...r.kernel.org,
	perex@...ex.cz, pierre-louis.bossart@...ux.dev,
	quic_wcheng@...cinc.com, syzkaller@...glegroups.com, tiwai@...e.com
Subject: Re: [PATCH] ALSA: usb-audio: Fix NULL pointer deference in
 try_to_register_card

On Tue, Oct 14, 2025 at 12:01:49PM +0800, Jiaming Zhang wrote:
> Hi Greg,
> 
> Thanks for the guidance. You're right, the root cause of this issue is
> that a USB audio device is created without a proper interface.
> 
> To fix this issue, I added a check for the NULL return value in
> try_to_register_card() before calling usb_interface_claimed().
> I have tested patch with the reproducer on the latest version (v6.18-rc1),
> the issue was not triggered again.
> 
> Please let me know if any changes are needed.
> 
> Best regards,
> Jiaming Zhang

Can you resend this without this text above the changelog comment?

> ---
> 
> In try_to_register_card(), the return value of usb_ifnum_to_if() is
> passed directly to usb_interface_claimed() without a NULL check, which
> will lead to a NULL pointer dereference when creating an invalid
> USB audio device. Fix this by adding a check to ensure the interface
> pointer is valid before passing it to usb_interface_claimed().
> 
> Reported-by: Jiaming Zhang <r772577952@...il.com>
> Signed-off-by: Jiaming Zhang <r772577952@...il.com>

And as you authored this, no need for "Reported-by:" :)

thanks,

greg k-h