Re: [PATCH] drm: Avoid NULL deference when disabling a plane from userspace

[Daniel Vetter <daniel@ffwll.ch>]

On Fri, Jun 13, 2014 at 03:22:28PM +0100, Chris Wilson wrote:
> To disable a plane, userspace passes in an framebuffer id of 0. This
> causes us to pass CRTC == NULL to setplane_internal, who promptly
> deferences it to grab the struct drm_device. Oops.
> 
> [ 1296.467327] BUG: unable to handle kernel NULL pointer dereference at   (null)
> [ 1296.467332] IP: [<c134dc51>] setplane_internal+0x11/0x280
> [ 1296.467338] *pde = 00000000
> [ 1296.467341] Oops: 0000 [#1] SMP
> [ 1296.467344] Modules linked in: ccm bnep bluetooth snd_hda_codec_hdmi snd_hda_codec_idt snd_hda_codec_generic snd_hda_intel arc4 iwldvm snd_hda_controller snd_hda_codec mac80211 snd_hwdep snd_seq snd_seq_device snd_pcm snd_timer iwlwifi sdhci_pci snd cfg80211 x86_pkg_temp_thermal hp_wmi sdhci sparse_keymap mmc_core crc32c_intel rfkill microcode hp_accel lpc_ich lis3lv02d wmi mfd_core serio_raw input_polldev soundcore e1000e ptp pps_core
> [ 1296.467367] CPU: 1 PID: 672 Comm: Xorg Tainted: G        W     3.15.0-rc8+ #351
> [ 1296.467369] Hardware name: Hewlett-Packard HP ProBook 6360b/1620, BIOS 68SCF Ver. B.42 12/29/2010
> [ 1296.467371] task: f423b5c0 ti: c2332000 task.ti: c2332000
> [ 1296.467374] EIP: 0060:[<c134dc51>] EFLAGS: 00013286 CPU: 1
> [ 1296.467376] EIP is at setplane_internal+0x11/0x280
> [ 1296.467378] EAX: 00000000 EBX: c2333e90 ECX: 00000000 EDX: f3165600
> [ 1296.467380] ESI: f430f400 EDI: 00000000 EBP: c2333e14 ESP: c2333dd4
> [ 1296.467382]  DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
> [ 1296.467384] CR0: 80050033 CR2: 00000000 CR3: 00159000 CR4: 000407d0
> [ 1296.467385] Stack:
> [ 1296.467387]  000200da 00000002 c2333de8 c15dc4a0 f430f400 c2333e00 c134c54f eeeeeeee
> [ 1296.467391]  f430f400 00000007 f416b480 c2333e14 00000000 c2333e90 f430f400 00000000
> [ 1296.467396]  c2333e4c c1350aed 00000000 00000000 00000000 00000000 00000000 00000000
> [ 1296.467400] Call Trace:
> [ 1296.467406]  [<c15dc4a0>] ? mutex_lock+0x10/0x28
> [ 1296.467408]  [<c134c54f>] ? _object_find+0x5f/0x90
> [ 1296.467413]  [<c1350aed>] drm_mode_setplane+0x10d/0x1f0
> [ 1296.467416]  [<c13509e0>] ? drm_mode_getplane+0x100/0x100
> [ 1296.467420]  [<c1342e4d>] drm_ioctl+0x1bd/0x4f0
> [ 1296.467423]  [<c13509e0>] ? drm_mode_getplane+0x100/0x100
> [ 1296.467427]  [<c111c023>] ? handle_mm_fault+0x5d3/0xb30
> [ 1296.467431]  [<c1118f31>] ? tlb_finish_mmu+0x11/0x40
> [ 1296.467435]  [<c1342c90>] ? drm_ioctl_flags+0x40/0x40
> [ 1296.467438]  [<c11593d2>] do_vfs_ioctl+0x2f2/0x4d0
> [ 1296.467443]  [<c1226512>] ? inode_has_perm.isra.32+0x32/0x40
> [ 1296.467446]  [<c122662f>] ? file_has_perm+0x7f/0x90
> [ 1296.467449]  [<c1226fec>] ? selinux_file_ioctl+0x4c/0xf0
> [ 1296.467452]  [<c1159610>] SyS_ioctl+0x60/0x90
> [ 1296.467456]  [<c15e578c>] sysenter_do_call+0x12/0x22
> [ 1296.467457] Code: 3f cf ff eb dd ba 3f 00 00 00 b8 d9 c9 7f c1 e8 e6 3f cf ff eb d9 8d 74 26 00 55 89 e5 57 56 53 83 ec 34 66 66 66 66 90 89 45 f0 <8b> 00 85 c9 89 d6 89 cb 89 45 ec 0f 84 16 01 00 00 8b 45 f0 e8
> [ 1296.467485] EIP: [<c134dc51>] setplane_internal+0x11/0x280 SS:ESP 0068:c2
> 
> Fixes regression from
> commit b02fd7fd8a541c3d590bfdda23365a927b507ceb
> Author: Matt Roper <matthew.d.roper@intel.com>
> Date:   Tue Jun 10 08:28:10 2014 -0700
> 
>     drm: Support legacy cursor ioctls via universal planes when possible (v4)

I'll add

"While at it move the plane parameter to the first position in
setplane_internal since that's the main object we're manipulating."

when merging. Ok?
-Daniel
> 
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: Pallavi G<pallavi.g@intel.com>
> Cc: Matt Roper <matthew.d.roper@intel.com>
> ---
>  drivers/gpu/drm/drm_crtc.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> index 5efac1f3be2d..a9cdb56a5301 100644
> --- a/drivers/gpu/drm/drm_crtc.c
> +++ b/drivers/gpu/drm/drm_crtc.c
> @@ -2189,8 +2189,8 @@ out:
>   *
>   * src_{x,y,w,h} are provided in 16.16 fixed point format
>   */
> -static int setplane_internal(struct drm_crtc *crtc,
> -			     struct drm_plane *plane,
> +static int setplane_internal(struct drm_plane *plane,
> +			     struct drm_crtc *crtc,
>  			     struct drm_framebuffer *fb,
>  			     int32_t crtc_x, int32_t crtc_y,
>  			     uint32_t crtc_w, uint32_t crtc_h,
> @@ -2198,7 +2198,7 @@ static int setplane_internal(struct drm_crtc *crtc,
>  			     uint32_t src_x, uint32_t src_y,
>  			     uint32_t src_w, uint32_t src_h)
>  {
> -	struct drm_device *dev = crtc->dev;
> +	struct drm_device *dev = plane->dev;
>  	struct drm_framebuffer *old_fb = NULL;
>  	int ret = 0;
>  	unsigned int fb_width, fb_height;
> @@ -2350,7 +2350,7 @@ int drm_mode_setplane(struct drm_device *dev, void *data,
>  	 * setplane_internal will take care of deref'ing either the old or new
>  	 * framebuffer depending on success.
>  	 */
> -	return setplane_internal(crtc, plane, fb,
> +	return setplane_internal(plane, crtc, fb,
>  				 plane_req->crtc_x, plane_req->crtc_y,
>  				 plane_req->crtc_w, plane_req->crtc_h,
>  				 plane_req->src_x, plane_req->src_y,
> @@ -2686,7 +2686,7 @@ static int drm_mode_cursor_universal(struct drm_crtc *crtc,
>  	 * setplane_internal will take care of deref'ing either the old or new
>  	 * framebuffer depending on success.
>  	 */
> -	ret = setplane_internal(crtc, crtc->cursor, fb,
> +	ret = setplane_internal(crtc->cursor, crtc, fb,
>  				crtc_x, crtc_y, crtc_w, crtc_h,
>  				0, 0, src_w, src_h);
>  
> -- 
> 2.0.0
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch