drm/ttm: Fix dummy res NULL ptr deref bug

In the Linux kernel, the following vulnerability has been resolved:

drm/ttm: Fix dummy res NULL ptr deref bug

Check the bo->resource value before accessing the resource
mem_type.

v2: Fix commit description unwrapped warning

<log snip>
[ 40.191227][ T184] general protection fault, probably for non-canonical address 0xdffffc0000000002: 0000 [#1] SMP KASAN PTI
[ 40.192995][ T184] KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017]
[ 40.194411][ T184] CPU: 1 PID: 184 Comm: systemd-udevd Not tainted 5.19.0-rc4-00721-gb297c22b7070 #1
[ 40.196063][ T184] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.0-debian-1.16.0-4 04/01/2014
[ 40.199605][ T184] RIP: 0010:ttm_bo_validate+0x1b3/0x240 [ttm]
[ 40.200754][ T184] Code: e8 72 c5 ff ff 83 f8 b8 74 d4 85 c0 75 54 49 8b 9e 58 01 00 00 48 b8 00 00 00 00 00 fc ff df 48 8d 7b 10 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84 c0 74 04 3c 03 7e 44 8b 53 10 31 c0 85 d2 0f 85 58
[ 40.203685][ T184] RSP: 0018:ffffc900006df0c8 EFLAGS: 00010202
[ 40.204630][ T184] RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 1ffff1102f4bb71b
[ 40.205864][ T184] RDX: 0000000000000002 RSI: ffffc900006df208 RDI: 0000000000000010
[ 40.207102][ T184] RBP: 1ffff920000dbe1a R08: ffffc900006df208 R09: 0000000000000000
[ 40.208394][ T184] R10: ffff88817a5f0000 R11: 0000000000000001 R12: ffffc900006df110
[ 40.209692][ T184] R13: ffffc900006df0f0 R14: ffff88817a5db800 R15: ffffc900006df208
[ 40.210862][ T184] FS: 00007f6b1d16e8c0(0000) GS:ffff88839d700000(0000) knlGS:0000000000000000
[ 40.212250][ T184] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 40.213275][ T184] CR2: 000055a1001d4ff0 CR3: 00000001700f4000 CR4: 00000000000006e0
[ 40.214469][ T184] Call Trace:
[ 40.214974][ T184] <TASK>
[ 40.215438][ T184] ? ttm_bo_bounce_temp_buffer+0x140/0x140 [ttm]
[ 40.216572][ T184] ? mutex_spin_on_owner+0x240/0x240
[ 40.217456][ T184] ? drm_vma_offset_add+0xaa/0x100 [drm]
[ 40.218457][ T184] ttm_bo_init_reserved+0x3d6/0x540 [ttm]
[ 40.219410][ T184] ? shmem_get_inode+0x744/0x980
[ 40.220231][ T184] ttm_bo_init_validate+0xb1/0x200 [ttm]
[ 40.221172][ T184] ? bo_driver_evict_flags+0x340/0x340 [drm_vram_helper]
[ 40.222530][ T184] ? ttm_bo_init_reserved+0x540/0x540 [ttm]
[ 40.223643][ T184] ? __do_sys_finit_module+0x11a/0x1c0
[ 40.224654][ T184] ? __shmem_file_setup+0x102/0x280
[ 40.234764][ T184] drm_gem_vram_create+0x305/0x480 [drm_vram_helper]
[ 40.235766][ T184] ? bo_driver_evict_flags+0x340/0x340 [drm_vram_helper]
[ 40.236846][ T184] ? __kasan_slab_free+0x108/0x180
[ 40.237650][ T184] drm_gem_vram_fill_create_dumb+0x134/0x340 [drm_vram_helper]
[ 40.238864][ T184] ? local_pci_probe+0xdf/0x180
[ 40.239674][ T184] ? drmm_vram_helper_init+0x400/0x400 [drm_vram_helper]
[ 40.240826][ T184] drm_client_framebuffer_create+0x19c/0x400 [drm]
[ 40.241955][ T184] ? drm_client_buffer_delete+0x200/0x200 [drm]
[ 40.243001][ T184] ? drm_client_pick_crtcs+0x554/0xb80 [drm]
[ 40.244030][ T184] drm_fb_helper_generic_probe+0x23f/0x940 [drm_kms_helper]
[ 40.245226][ T184] ? __cond_resched+0x1c/0xc0
[ 40.245987][ T184] ? drm_fb_helper_memory_range_to_clip+0x180/0x180 [drm_kms_helper]
[ 40.247316][ T184] ? mutex_unlock+0x80/0x100
[ 40.248005][ T184] ? __mutex_unlock_slowpath+0x2c0/0x2c0
[ 40.249083][ T184] drm_fb_helper_single_fb_probe+0x907/0xf00 [drm_kms_helper]
[ 40.250314][ T184] ? drm_fb_helper_check_var+0x1180/0x1180 [drm_kms_helper]
[ 40.251540][ T184] ? __cond_resched+0x1c/0xc0
[ 40.252321][ T184] ? mutex_lock+0x9f/0x100
[ 40.253062][ T184] __drm_fb_helper_initial_config_and_unlock+0xb9/0x2c0 [drm_kms_helper]
[ 40.254394][ T184] drm_fbdev_client_hotplug+0x56f/0x840 [drm_kms_helper]
[ 40.255477][ T184] drm_fbdev_generic_setup+0x165/0x3c0 [drm_kms_helper]
[ 40.256607][ T184] bochs_pci_probe+0x6b7/0x900 [bochs]
[
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