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Subject: Re: [PATCH v2] drm/ttm: Fix dummy res NULL ptr deref bug
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To: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@amd.com>
References: <20220727053032.3668-1-Arunpravin.PaneerSelvam@amd.com>
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Hi Arunpravin,

Às 02:30 de 27/07/22, Arunpravin Paneer Selvam escreveu:
> 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]
> [   40.257515][  T184]  ? _raw_spin_lock_irqsave+0x87/0x100
> [   40.258312][  T184]  ? bochs_hw_init+0x480/0x480 [bochs]
> [   40.259244][  T184]  ? bochs_hw_init+0x480/0x480 [bochs]
> [   40.260186][  T184]  local_pci_probe+0xdf/0x180
> [   40.260928][  T184]  pci_call_probe+0x15f/0x500
> [   40.265798][  T184]  ? _raw_spin_lock+0x81/0x100
> [   40.266508][  T184]  ? pci_pm_suspend_noirq+0x980/0x980
> [   40.267322][  T184]  ? pci_assign_irq+0x81/0x280
> [   40.268096][  T184]  ? pci_match_device+0x351/0x6c0
> [   40.268883][  T184]  ? kernfs_put+0x18/0x40
> [   40.269611][  T184]  pci_device_probe+0xee/0x240
> [   40.270352][  T184]  really_probe+0x435/0xa80
> [   40.271021][  T184]  __driver_probe_device+0x2ab/0x480
> [   40.271828][  T184]  driver_probe_device+0x49/0x140
> [   40.272627][  T184]  __driver_attach+0x1bd/0x4c0
> [   40.273372][  T184]  ? __device_attach_driver+0x240/0x240
> [   40.274273][  T184]  bus_for_each_dev+0x11e/0x1c0
> [   40.275080][  T184]  ? subsys_dev_iter_exit+0x40/0x40
> [   40.275951][  T184]  ? klist_add_tail+0x132/0x280
> [   40.276767][  T184]  bus_add_driver+0x39b/0x580
> [   40.277574][  T184]  driver_register+0x20f/0x3c0
> [   40.278281][  T184]  ? 0xffffffffc04a2000
> [   40.278894][  T184]  do_one_initcall+0x8a/0x300
> [   40.279642][  T184]  ? trace_event_raw_event_initcall_level+0x1c0/0x1c0
> [   40.280707][  T184]  ? kasan_unpoison+0x23/0x80
> [   40.281479][  T184]  ? kasan_unpoison+0x23/0x80
> [   40.282197][  T184]  do_init_module+0x190/0x640
> [   40.282926][  T184]  load_module+0x221b/0x2780
> [   40.283611][  T184]  ? layout_and_allocate+0x5c0/0x5c0
> [   40.284401][  T184]  ? kernel_read_file+0x286/0x6c0
> [   40.285216][  T184]  ? __x64_sys_fspick+0x2c0/0x2c0
> [   40.286043][  T184]  ? mmap_region+0x4e7/0x1300
> [   40.286832][  T184]  ? __do_sys_finit_module+0x11a/0x1c0
> [   40.287743][  T184]  __do_sys_finit_module+0x11a/0x1c0
> [   40.288636][  T184]  ? __ia32_sys_init_module+0xc0/0xc0
> [   40.289557][  T184]  ? __seccomp_filter+0x15e/0xc80
> [   40.290341][  T184]  ? vm_mmap_pgoff+0x185/0x240
> [   40.291060][  T184]  do_syscall_64+0x3b/0xc0
> [   40.291763][  T184]  entry_SYSCALL_64_after_hwframe+0x46/0xb0
> [   40.292678][  T184] RIP: 0033:0x7f6b1d6279b9
> [   40.293438][  T184] Code: 00 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d a7 54 0c 00 f7 d8 64 89 01 48
> [   40.296302][  T184] RSP: 002b:00007ffe7f51b798 EFLAGS: 00000246 ORIG_RAX: 0000000000000139
> [   40.297633][  T184] RAX: ffffffffffffffda RBX: 00005642dcca2880 RCX: 00007f6b1d6279b9
> [   40.298890][  T184] RDX: 0000000000000000 RSI: 00007f6b1d7b2e2d RDI: 0000000000000016
> [   40.300199][  T184] RBP: 0000000000020000 R08: 0000000000000000 R09: 00005642dccd5530
> [   40.301547][  T184] R10: 0000000000000016 R11: 0000000000000246 R12: 00007f6b1d7b2e2d
> [   40.302698][  T184] R13: 0000000000000000 R14: 00005642dcca4230 R15: 00005642dcca2880
> 
> Signed-off-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@amd.com>
> Reported-by: kernel test robot <oliver.sang@intel.com>
> ---
>  drivers/gpu/drm/ttm/ttm_bo.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
> index c1bd006a5525..590110fdf59c 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> @@ -912,7 +912,7 @@ int ttm_bo_validate(struct ttm_buffer_object *bo,
>  	/*
>  	 * We might need to add a TTM.
>  	 */
> -	if (bo->resource->mem_type == TTM_PL_SYSTEM) {
> +	if (!bo->resource || bo->resource->mem_type == TTM_PL_SYSTEM) {
>  		ret = ttm_tt_create(bo, true);
>  		if (ret)
>  			return ret;


bo->resource is accessed a bit earlier in the same function at

	ttm_resource_compat(bo->resource, placement)

I wonder if this would need to be check for NULL as well.