linux-kernel - Re: [PATCH v1 0/3] usb: gadget: uvc: stability fixes on STREAMOFF.

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Message-ID: <20231005082327.GC13853@pendragon.ideasonboard.com>
Date:   Thu, 5 Oct 2023 11:23:27 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Michael Grzeschik <mgr@...gutronix.de>
Cc:     Avichal Rakesh <arakesh@...gle.com>,
        Daniel Scally <dan.scally@...asonboard.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        jchowdhary@...gle.com, etalvala@...gle.com,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 0/3] usb: gadget: uvc: stability fixes on STREAMOFF.

On Tue, Oct 03, 2023 at 01:09:06PM +0200, Michael Grzeschik wrote:
> 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.

I think they got merged too soon :-( We could fix things on top, but
there's very little time to do so for v6.7.

> 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] ============================================
> [   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_video_complete+0x44/0x2e0
> [   47.210172]
> [   47.210172] but task is already holding lock:
> [   47.216687] ffffff8009560928 (&video->req_lock){....}-{3:3}, at: uvcg_video_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,

Laurent Pinchart