[PATCH 2/6] drm/gud: Fix UBSAN warning

[Thomas Zimmermann]

Am 22.11.22 um 21:58 schrieb Noralf Trønnes via B4 Submission Endpoint:
> From: Noralf Trønnes <noralf at tronnes.org>
> 
> UBSAN complains about invalid value for bool:
> 
> [  101.165172] [drm] Initialized gud 1.0.0 20200422 for 2-3.2:1.0 on minor 1
> [  101.213360] gud 2-3.2:1.0: [drm] fb1: guddrmfb frame buffer device
> [  101.213426] usbcore: registered new interface driver gud
> [  101.989431] ================================================================================
> [  101.989441] UBSAN: invalid-load in /home/pi/linux/include/linux/iosys-map.h:253:9
> [  101.989447] load of value 121 is not a valid value for type '_Bool'
> [  101.989451] CPU: 1 PID: 455 Comm: kworker/1:6 Not tainted 5.18.0-rc5-gud-5.18-rc5 #3
> [  101.989456] Hardware name: Hewlett-Packard HP EliteBook 820 G1/1991, BIOS L71 Ver. 01.44 04/12/2018
> [  101.989459] Workqueue: events_long gud_flush_work [gud]
> [  101.989471] Call Trace:
> [  101.989474]  <TASK>
> [  101.989479]  dump_stack_lvl+0x49/0x5f
> [  101.989488]  dump_stack+0x10/0x12
> [  101.989493]  ubsan_epilogue+0x9/0x3b
> [  101.989498]  __ubsan_handle_load_invalid_value.cold+0x44/0x49
> [  101.989504]  dma_buf_vmap.cold+0x38/0x3d
> [  101.989511]  ? find_busiest_group+0x48/0x300
> [  101.989520]  drm_gem_shmem_vmap+0x76/0x1b0 [drm_shmem_helper]
> [  101.989528]  drm_gem_shmem_object_vmap+0x9/0xb [drm_shmem_helper]
> [  101.989535]  drm_gem_vmap+0x26/0x60 [drm]
> [  101.989594]  drm_gem_fb_vmap+0x47/0x150 [drm_kms_helper]
> [  101.989630]  gud_prep_flush+0xc1/0x710 [gud]
> [  101.989639]  ? _raw_spin_lock+0x17/0x40
> [  101.989648]  gud_flush_work+0x1e0/0x430 [gud]
> [  101.989653]  ? __switch_to+0x11d/0x470
> [  101.989664]  process_one_work+0x21f/0x3f0
> [  101.989673]  worker_thread+0x200/0x3e0
> [  101.989679]  ? rescuer_thread+0x390/0x390
> [  101.989684]  kthread+0xfd/0x130
> [  101.989690]  ? kthread_complete_and_exit+0x20/0x20
> [  101.989696]  ret_from_fork+0x22/0x30
> [  101.989706]  </TASK>
> [  101.989708] ================================================================================
> 
> The source of this warning is in iosys_map_clear() called from
> dma_buf_vmap(). It conditionally sets values based on map->is_iomem. The
> iosys_map variables are allocated uninitialized on the stack leading to
> ->is_iomem having all kinds of values and not only 0/1.
> 
> Fix this by zeroing the iosys_map variables.
> 
> Fixes: 40e1a70b4aed ("drm: Add GUD USB Display driver")
> Cc: <stable at vger.kernel.org> # v5.18+
> Signed-off-by: Noralf Trønnes <noralf at tronnes.org>

Reviewed-by: Thomas Zimmermann <tzimmermann at suse.de>

> ---
>   drivers/gpu/drm/gud/gud_pipe.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/gud/gud_pipe.c b/drivers/gpu/drm/gud/gud_pipe.c
> index 7c6dc2bcd14a..61f4abaf1811 100644
> --- a/drivers/gpu/drm/gud/gud_pipe.c
> +++ b/drivers/gpu/drm/gud/gud_pipe.c
> @@ -157,8 +157,8 @@ static int gud_prep_flush(struct gud_device *gdrm, struct drm_framebuffer *fb,
>   {
>   	struct dma_buf_attachment *import_attach = fb->obj[0]->import_attach;
>   	u8 compression = gdrm->compression;
> -	struct iosys_map map[DRM_FORMAT_MAX_PLANES];
> -	struct iosys_map map_data[DRM_FORMAT_MAX_PLANES];
> +	struct iosys_map map[DRM_FORMAT_MAX_PLANES] = { };
> +	struct iosys_map map_data[DRM_FORMAT_MAX_PLANES] = { };
>   	struct iosys_map dst;
>   	void *vaddr, *buf;
>   	size_t pitch, len;
> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev
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