linux-kernel - Re: [PATCH] drm/radeon: don't add files at control minor debugfs directory

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Message-ID: <20161205072709.zcoja6eak2sjgd2k@phenom.ffwll.local>
Date:   Mon, 5 Dec 2016 08:27:09 +0100
From:   Daniel Vetter <daniel@...ll.ch>
To:     Nicolai Stange <nicstange@...il.com>
Cc:     Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        Daniel Vetter <daniel.vetter@...el.com>,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH] drm/radeon: don't add files at control minor debugfs
 directory

On Sat, Dec 03, 2016 at 03:47:00PM +0100, Nicolai Stange wrote:
> Since commit 8a357d10043c ("drm: Nerf DRM_CONTROL nodes"), a
> struct drm_device's ->control member is always NULL.
> 
> In the case of CONFIG_DEBUG_FS=y, radeon_debugfs_add_files() accesses
> ->control->debugfs_root though. This results in the following Oops:
> 
>   BUG: unable to handle kernel NULL pointer dereference at 0000000000000018
>   IP: radeon_debugfs_add_files+0x90/0x100 [radeon]
>   PGD 0
>   Oops: 0000 [#1] SMP
>   [...]
>   Call Trace:
>    ? work_on_cpu+0xb0/0xb0
>    radeon_fence_driver_init+0x120/0x150 [radeon]
>    si_init+0x122/0xd50 [radeon]
>    ? _raw_spin_unlock_irq+0x2c/0x40
>    ? device_pm_check_callbacks+0xb3/0xc0
>    radeon_device_init+0x958/0xda0 [radeon]
>    radeon_driver_load_kms+0x9a/0x210 [radeon]
>    drm_dev_register+0xa9/0xd0 [drm]
>    drm_get_pci_dev+0x9c/0x1e0 [drm]
>    radeon_pci_probe+0xb8/0xe0 [radeon]
>   [...]
> 
> Fix this by omitting the drm_debugfs_create_files() call for the
> control minor debugfs directory which is now non-existent anyway.
> 
> Fixes: 8a357d10043c ("drm: Nerf DRM_CONTROL nodes")
> Signed-off-by: Nicolai Stange <nicstange@...il.com>

Applied to drm-misc with Dave's irc ack, thanks for your patch.
-Daniel

> ---
> Tested on top of next-20161202.
> That 8a357d10043c ("drm: Nerf DRM_CONTROL nodes")
> is in next since 20161201.
> 
>  drivers/gpu/drm/radeon/radeon_device.c | 6 ------
>  1 file changed, 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/radeon/radeon_device.c b/drivers/gpu/drm/radeon/radeon_device.c
> index 60a8920..8a1df2a 100644
> --- a/drivers/gpu/drm/radeon/radeon_device.c
> +++ b/drivers/gpu/drm/radeon/radeon_device.c
> @@ -1949,9 +1949,6 @@ int radeon_debugfs_add_files(struct radeon_device *rdev,
>  	rdev->debugfs_count = i;
>  #if defined(CONFIG_DEBUG_FS)
>  	drm_debugfs_create_files(files, nfiles,
> -				 rdev->ddev->control->debugfs_root,
> -				 rdev->ddev->control);
> -	drm_debugfs_create_files(files, nfiles,
>  				 rdev->ddev->primary->debugfs_root,
>  				 rdev->ddev->primary);
>  #endif
> @@ -1966,9 +1963,6 @@ static void radeon_debugfs_remove_files(struct radeon_device *rdev)
>  	for (i = 0; i < rdev->debugfs_count; i++) {
>  		drm_debugfs_remove_files(rdev->debugfs[i].files,
>  					 rdev->debugfs[i].num_files,
> -					 rdev->ddev->control);
> -		drm_debugfs_remove_files(rdev->debugfs[i].files,
> -					 rdev->debugfs[i].num_files,
>  					 rdev->ddev->primary);
>  	}
>  #endif
> -- 
> 2.10.2
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@...ts.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

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