linux-kernel - Re: Oops in 3.10.99 -- NULL pointer dereference in radeon_fence

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Date:	Mon, 7 Mar 2016 14:58:51 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Christian König <christian.koenig@....com>
Cc:	andersen@...epoet.org, linux-kernel <linux-kernel@...r.kernel.org>,
	Nicolai Hähnle <nicolai.haehnle@....com>,
	stable@...r.kernel.org
Subject: Re: Oops in 3.10.99 -- NULL pointer dereference in radeon_fence_ref

On Mon, Mar 07, 2016 at 10:06:47PM +0100, Christian König wrote:
> Am 07.03.2016 um 21:46 schrieb Greg Kroah-Hartman:
> >On Sun, Mar 06, 2016 at 07:50:14PM -0700, Erik Andersen wrote:
> >>The following patch to radeon_sa_bo_new that
> >>went into 3.10.99
> >>
> >>   commit 8d5e1e5af0c667545c202e8f4051f77aa3bf31b7
> >>   Author: Nicolai HÃ¤hnle <nicolai.haehnle@....com>
> >>   Date:   Fri Feb 5 14:35:53 2016 -0500
> >>     drm/radeon: hold reference to fences in radeon_sa_bo_new
> >>     commit f6ff4f67cdf8455d0a4226eeeaf5af17c37d05eb upstream.
> >>
> >>is triggering an Oops for me right when xscreensaver
> >>first began doing 3D stuff.  After reverting this
> >>patch, xscreensaver has been happily running 3D stuff.
> >>
> >>Mar  6 18:00:43 sage kernel: BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
> >>Mar  6 18:00:43 sage kernel: IP: [<ffffffffa010345d>] radeon_fence_ref+0xd/0x50 [radeon]
> >>Mar  6 18:00:43 sage kernel: PGD 799e1d067 PUD 819186067 PMD 0
> >>Mar  6 18:00:43 sage kernel: Oops: 0002 [#1] SMP
> >>
> >>Mar  6 18:00:43 sage kernel: Stack:
> >>Mar  6 18:00:43 sage kernel:  ffffffffa01607ec ffff88108a4e8000 ffff88108a4e8000 ffff880888fbc000
> >>Mar  6 18:00:43 sage kernel:  ffff880ecbf11c78 0000fe2001000006 0000000000000000 0020000000000100
> >>Mar  6 18:00:43 sage kernel:  00000000000d1200 ffff880ecbf11c14 0000000000000000 0000000000000000
> >>Mar  6 18:00:43 sage kernel: Call Trace:
> >>Mar  6 18:00:43 sage kernel:  [<ffffffffa01607ec>] ? radeon_sa_bo_new+0x2ac/0x4f0 [radeon]
> >>Mar  6 18:00:43 sage kernel:  [<ffffffffa005fc9d>] ? ttm_eu_list_ref_sub+0x3d/0x60 [ttm]
> >>Mar  6 18:00:43 sage kernel:  [<ffffffffa0117c49>] radeon_ib_get+0x39/0x110 [radeon]
> >>Mar  6 18:00:43 sage kernel:  [<ffffffffa011a4ea>] radeon_cs_ioctl+0x69a/0xa70 [radeon]
> >>Mar  6 18:00:43 sage kernel:  [<ffffffffa008e2d2>] drm_ioctl+0x512/0x650 [drm]
> >>Mar  6 18:00:43 sage kernel:  [<ffffffff810a46e1>] ? do_futex+0x111/0xc30
> >>Mar  6 18:00:43 sage kernel:  [<ffffffff81182a45>] do_vfs_ioctl+0x305/0x520
> >>Mar  6 18:00:43 sage kernel:  [<ffffffff8107cd39>] ? vtime_account_user+0x69/0x80
> >>Mar  6 18:00:43 sage kernel:  [<ffffffff81182ce1>] SyS_ioctl+0x81/0xa0
> >>Mar  6 18:00:43 sage kernel:  [<ffffffff8178210f>] tracesys+0xe1/0xe6
> >>
> >>$ lspci | grep VGA
> >>03:00.0 VGA compatible controller: Advanced Micro Devices, Inc.
> >>[AMD/ATI] Redwood XT [Radeon HD 5670/5690/5730]
> >Next time, please cc: the people responsible for that patch as well...
> >
> >I can revert it, but maybe something else is going on here?  Do you have
> >this same problem on 3.14, and 4.5-rc7?
> 
> Hi Greg,
> 
> yes that's an already known issue. Feel free to revert that one for now.
> 
> I got it on my TODO list to provide a fixed patch for older kernel, but that
> can take a while.
> 
> For the background Nicolais patch is correct, but assumes that
> radeon_fence_unref() can safely take NULL as the fence which is not the case
> for older kernels.

Ok, thanks, now reverted.

greg k-h