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Date:   Tue, 3 Oct 2023 13:09:06 +0200
From:   Michael Grzeschik <mgr@pengutronix.de>
To:     Avichal Rakesh <arakesh@google.com>
Cc:     Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        Daniel Scally <dan.scally@ideasonboard.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        jchowdhary@google.com, etalvala@google.com,
        linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1 0/3] usb: gadget: uvc: stability fixes on STREAMOFF.
Message-ID: <ZRv2UnKztgyqk2pt@pengutronix.de>
References: <20230930184821.310143-1-arakesh@google.com>
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Hi

On Sat, Sep 30, 2023 at 11:48:18AM -0700, Avichal Rakesh wrote:
>We have been seeing two main stability issues that uvc gadget driver
>runs into when stopping streams:
> 1. Attempting to queue usb_requests to a disabled usb_ep
> 2. use-after-free issue for inflight usb_requests
>
>The three patches below fix the two issues above. Patch 1/3 fixes the
>first issue, and Patch 2/3 and 3/3 fix the second issue.
>
>Avichal Rakesh (3):
>  usb: gadget: uvc: prevent use of disabled endpoint
>  usb: gadget: uvc: Allocate uvc_requests one at a time
>  usb: gadget: uvc: Fix use-after-free for inflight usb_requests
>
> drivers/usb/gadget/function/f_uvc.c     |  11 +-
> drivers/usb/gadget/function/f_uvc.h     |   2 +-
> drivers/usb/gadget/function/uvc.h       |   6 +-
> drivers/usb/gadget/function/uvc_v4l2.c  |  21 ++-
> drivers/usb/gadget/function/uvc_video.c | 189 +++++++++++++++++-------
> 5 files changed, 164 insertions(+), 65 deletions(-)

These patches are not applying on gregkh/usb-testing since
Greg did take my patches first. I have already rebased them.

In the updated version I the stack runs into the
following error, when enabling lockdep. Could you
try your version with lockdep enabled?

[   41.278520] configfs-gadget.vz gadget.0: uvc: reset UVC
[   47.156261] configfs-gadget.vz gadget.0: uvc: uvc_function_set_alt(2, 0)
[   47.169177]
[   47.170903] =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
[   47.176857] WARNING: possible recursive locking detected
[   47.182798] 6.5.0-20230919-1+ #19 Tainted: G         C
[   47.189323] --------------------------------------------
[   47.195256] vzuvcd/412 is trying to acquire lock:
[   47.200511] ffffff8009560928 (&video->req_lock){....}-{3:3}, at: uvc_vid=
eo_complete+0x44/0x2e0
[   47.210172]
[   47.210172] but task is already holding lock:
[   47.216687] ffffff8009560928 (&video->req_lock){....}-{3:3}, at: uvcg_vi=
deo_enable+0x2d0/0x5c0
[   47.226333]
[   47.226333] other info that might help us debug this:
[   47.233625]  Possible unsafe locking scenario:
[   47.233625]
[   47.240242]        CPU0
[   47.242974]        ----
[   47.245709]   lock(&video->req_lock);
[   47.249802]   lock(&video->req_lock);
[   47.253897]
[   47.253897]  *** DEADLOCK ***
[   47.253897]
[   47.260511]  May be due to missing lock nesting notation
[   47.260511]


Regards,
Michael

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